Fix imdb.load_data for np v1.16.3
Fix imdb.load_data for np v1.16.3

https://github.com/keras-team/keras/pull/12714

Numpy 1.16.3 changed the default value for the allow_pickle flag.

So this load call breaks.

https://nvd.nist.gov/vuln/detail/CVE-2019-6446

https://github.com/numpy/numpy/blob/v1.16.2/numpy/lib/npyio.py#L288
https://github.com/numpy/numpy/blob/v1.16.3/numpy/lib/npyio.py#L292

`np.__version__` = 1.16.3
`keras.__version__` = 2.2.4
keras.datasets.imdb.load_data()

```
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-2-154d5969a0d5> in <module>
----> 1 k.datasets.imdb.load_data()

~/venv3/lib/python3.6/site-packages/keras/datasets/imdb.py in load_data(path, num_words, skip_top, maxlen, seed, start_char, oov_char, index_from, **kwargs)
     57                     file_hash='599dadb1135973df5b59232a0e9a887c')
     58     with np.load(path) as f:
---> 59         x_train, labels_train = f['x_train'], f['y_train']
     60         x_test, labels_test = f['x_test'], f['y_test']
     61

~/venv3/lib/python3.6/site-packages/numpy/lib/npyio.py in __getitem__(self, key)
    260                 return format.read_array(bytes,
    261                                          allow_pickle=self.allow_pickle,
--> 262                                          pickle_kwargs=self.pickle_kwargs)
    263             else:
    264                 return self.zip.read(key)

~/venv3/lib/python3.6/site-packages/numpy/lib/format.py in read_array(fp, allow_pickle, pickle_kwargs)
    690         # The array contained Python objects. We need to unpickle the data.
    691         if not allow_pickle:
--> 692             raise ValueError("Object arrays cannot be loaded when "
    693                              "allow_pickle=False")
    694         if pickle_kwargs is None:

ValueError: Object arrays cannot be loaded when allow_pickle=False
```
PiperOrigin-RevId: 244705570

davidzchen/tensorflow,Intel-tensorflow/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,tensorflow/tensorflow-pywrap_saved_model,gautam1858/tensorflow,arborh/tensorflow,petewarden/tensorflow,renyi533/tensorflow,frreiss/tensorflow-fred,aldian/tensorflow,gunan/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,sarvex/tensorflow,alsrgv/tensorflow,ppwwyyxx/tensorflow,chemelnucfin/tensorflow,Intel-tensorflow/tensorflow,aam-at/tensorflow,Intel-Corporation/tensorflow,renyi533/tensorflow,petewarden/tensorflow,arborh/tensorflow,Intel-Corporation/tensorflow,sarvex/tensorflow,ghchinoy/tensorflow,cxxgtxy/tensorflow,Intel-Corporation/tensorflow,chemelnucfin/tensorflow,frreiss/tensorflow-fred,adit-chandra/tensorflow,freedomtan/tensorflow,alsrgv/tensorflow,tensorflow/tensorflow-pywrap_saved_model,DavidNorman/tensorflow,renyi533/tensorflow,ghchinoy/tensorflow,chemelnucfin/tensorflow,alsrgv/tensorflow,frreiss/tensorflow-fred,tensorflow/tensorflow-experimental_link_static_libraries_once,yongtang/tensorflow,paolodedios/tensorflow,gautam1858/tensorflow,aam-at/tensorflow,frreiss/tensorflow-fred,karllessard/tensorflow,yongtang/tensorflow,freedomtan/tensorflow,aam-at/tensorflow,adit-chandra/tensorflow,frreiss/tensorflow-fred,freedomtan/tensorflow,renyi533/tensorflow,ghchinoy/tensorflow,davidzchen/tensorflow,renyi533/tensorflow,ghchinoy/tensorflow,arborh/tensorflow,davidzchen/tensorflow,annarev/tensorflow,DavidNorman/tensorflow,sarvex/tensorflow,aldian/tensorflow,petewarden/tensorflow,cxxgtxy/tensorflow,tensorflow/tensorflow,davidzchen/tensorflow,xzturn/tensorflow,DavidNorman/tensorflow,petewarden/tensorflow,yongtang/tensorflow,freedomtan/tensorflow,gunan/tensorflow,yongtang/tensorflow,ghchinoy/tensorflow,cxxgtxy/tensorflow,xzturn/tensorflow,xzturn/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,jhseu/tensorflow,adit-chandra/tensorflow,alsrgv/tensorflow,cxxgtxy/tensorflow,alsrgv/tensorflow,tensorflow/tensorflow,tensorflow/tensorflow,tensorflow/tensorflow-pywrap_saved_model,frreiss/tensorflow-fred,paolodedios/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,gautam1858/tensorflow,freedomtan/tensorflow,karllessard/tensorflow,tensorflow/tensorflow-pywrap_saved_model,DavidNorman/tensorflow,davidzchen/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,arborh/tensorflow,gunan/tensorflow,paolodedios/tensorflow,petewarden/tensorflow,arborh/tensorflow,karllessard/tensorflow,frreiss/tensorflow-fred,cxxgtxy/tensorflow,annarev/tensorflow,cxxgtxy/tensorflow,aam-at/tensorflow,davidzchen/tensorflow,Intel-tensorflow/tensorflow,gunan/tensorflow,frreiss/tensorflow-fred,adit-chandra/tensorflow,Intel-Corporation/tensorflow,paolodedios/tensorflow,gautam1858/tensorflow,adit-chandra/tensorflow,arborh/tensorflow,jhseu/tensorflow,Intel-tensorflow/tensorflow,annarev/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,renyi533/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,chemelnucfin/tensorflow,ppwwyyxx/tensorflow,adit-chandra/tensorflow,DavidNorman/tensorflow,tensorflow/tensorflow,arborh/tensorflow,gunan/tensorflow,aldian/tensorflow,xzturn/tensorflow,aldian/tensorflow,ppwwyyxx/tensorflow,aam-at/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,annarev/tensorflow,Intel-tensorflow/tensorflow,paolodedios/tensorflow,sarvex/tensorflow,adit-chandra/tensorflow,jhseu/tensorflow,DavidNorman/tensorflow,paolodedios/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,aam-at/tensorflow,gautam1858/tensorflow,xzturn/tensorflow,sarvex/tensorflow,DavidNorman/tensorflow,freedomtan/tensorflow,aldian/tensorflow,tensorflow/tensorflow,tensorflow/tensorflow-pywrap_saved_model,annarev/tensorflow,sarvex/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,aam-at/tensorflow,renyi533/tensorflow,tensorflow/tensorflow,gautam1858/tensorflow,tensorflow/tensorflow-pywrap_saved_model,tensorflow/tensorflow-pywrap_saved_model,alsrgv/tensorflow,jhseu/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,adit-chandra/tensorflow,ppwwyyxx/tensorflow,renyi533/tensorflow,renyi533/tensorflow,chemelnucfin/tensorflow,yongtang/tensorflow,ppwwyyxx/tensorflow,alsrgv/tensorflow,tensorflow/tensorflow-experimental_link_static_libraries_once,davidzchen/tensorflow,ghchinoy/tensorflow,cxxgtxy/tensorflow,DavidNorman/tensorflow,chemelnucfin/tensorflow,Intel-tensorflow/tensorflow,Intel-tensorflow/tensorflow,alsrgv/tensorflow,gautam1858/tensorflow,ghchinoy/tensorflow,alsrgv/tensorflow,adit-chandra/tensorflow,jhseu/tensorflow,ppwwyyxx/tensorflow,ppwwyyxx/tensorflow,paolodedios/tensorflow,ghchinoy/tensorflow,annarev/tensorflow,Intel-tensorflow/tensorflow,alsrgv/tensorflow,yongtang/tensorflow,freedomtan/tensorflow,Intel-tensorflow/tensorflow,davidzchen/tensorflow,tensorflow/tensorflow,xzturn/tensorflow,paolodedios/tensorflow,tensorflow/tensorflow,adit-chandra/tensorflow,tensorflow/tensorflow-pywrap_tf_optimizer,adit-chandra/tensorflow,ghchinoy/tensorflow,tensorflow/tensorflow-pywrap_tf_opt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