[SPARK-35682][PYTHON][TESTS] Pin mypy==0.812 in GitHub Actions CI
[SPARK-35682][PYTHON][TESTS] Pin mypy==0.812 in GitHub Actions CI

### What changes were proposed in this pull request?

Seems like the new MyPy version was released (0.901) and it broke the CI: https://github.com/python/mypy/releases.

```
python/pyspark/pandas/indexes/base.py:2007: error: Argument 1 to "from_tuples" of "MultiIndex" has incompatible type "Index"; expected "List[Tuple[Any, ...]]"
python/pyspark/testing/pandasutils.py:41: error: Library stubs not installed for "tabulate" (or incompatible with Python 3.6)
python/pyspark/testing/pandasutils.py:41: note: Hint: "python3 -m pip install types-tabulate"
python/pyspark/testing/pandasutils.py:41: note: (or run "mypy --install-types" to install all missing stub packages)
python/pyspark/testing/pandasutils.py:41: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
Found 2 errors in 2 files (checked 312 source files)
```

I tried to fix these instances and pin it to the latest version (0.901). However, I realised that `python/pyspark/pandas/indexes/base.py:2007` has a logic issue (see https://github.com/databricks/koalas/pull/1325#discussion_r647889901 and https://github.com/databricks/koalas/pull/1325#discussion_r647890007) which cannot be fixed quickly.

Therefore, I decided to pin it to the previous version we used before for now, in order to unblock other PRs builds.

### Why are the changes needed?

To unblock other PRs.

### Does this PR introduce _any_ user-facing change?

No, dev-only.

### How was this patch tested?

I tested in my local but it has to be tested and passed in GitHub Actions in this PR.

Closes #32829 from HyukjinKwon/SPARK-35682.

Authored-by: Hyukjin Kwon <2680965ad5aae29275c8fb10150cb10f5554e78b@apache.org>
Signed-off-by: Hyukjin Kwon <2680965ad5aae29275c8fb10150cb10f5554e78b@apache.org>

chuckchen/spark,zero323/spark,mahak/spark,mahak/spark,WeichenXu123/spark,maropu/spark,apache/spark,xuanyuanking/spark,mahak/spark,gengliangwang/spark,vinodkc/spark,xuanyuanking/spark,cloud-fan/spark,zzcclp/spark,WeichenXu123/spark,milliman/spark,wangyum/spark,HyukjinKwon/spark,witgo/spark,maropu/spark,ueshin/apache-spark,srowen/spark,chuckchen/spark,taroplus/spark,hvanhovell/spark,nchammas/spark,cloud-fan/spark,wangmiao1981/spark,rednaxelafx/apache-spark,vinodkc/spark,jiangxb1987/spark,zzcclp/spark,JoshRosen/spark,rednaxelafx/apache-spark,xuanyuanking/spark,jiangxb1987/spark,dongjoon-hyun/spark,zzcclp/spark,jiangxb1987/spark,zzcclp/spark,cloud-fan/spark,JoshRosen/spark,shaneknapp/spark,rednaxelafx/apache-spark,ueshin/apache-spark,gengliangwang/spark,ueshin/apache-spark,gengliangwang/spark,jiangxb1987/spark,rednaxelafx/apache-spark,maropu/spark,hvanhovell/spark,holdenk/spark,shaneknapp/spark,HyukjinKwon/spark,maropu/spark,cloud-fan/spark,mahak/spark,hvanhovell/spark,dongjoon-hyun/spark,HyukjinKwon/spark,milliman/spark,nchammas/spark,JoshRosen/spark,witgo/spark,HyukjinKwon/spark,rednaxelafx/apache-spark,maropu/spark,zero323/spark,dongjoon-hyun/spark,vinodkc/spark,witgo/spark,vinodkc/spark,holdenk/spark,milliman/spark,cloud-fan/spark,shaneknapp/spark,holdenk/spark,zero323/spark,HyukjinKwon/spark,hvanhovell/spark,taroplus/spark,jiangxb1987/spark,apache/spark,hvanhovell/spark,WeichenXu123/spark,chuckchen/spark,srowen/spark,srowen/spark,apache/spark,witgo/spark,apache/spark,HyukjinKwon/spark,chuckchen/spark,mahak/spark,nchammas/spark,vinodkc/spark,taroplus/spark,gengliangwang/spark,apache/spark,rednaxelafx/apache-spark,JoshRosen/spark,nchammas/spark,xuanyuanking/spark,chuckchen/spark,zzcclp/spark,wangmiao1981/spark,wangyum/spark,zzcclp/spark,shaneknapp/spark,srowen/spark,taroplus/spark,gengliangwang/spark,WeichenXu123/spark,taroplus/spark,hvanhovell/spark,mahak/spark,wangyum/spark,apache/spark,ueshin/apache-spark,cloud-fan/spark,xuanyuanking/spark,shaneknapp/spark,hvanhovell/spark,apache/spark,mahak/spark,holdenk/spark,shaneknapp/spark,jiangxb1987/spark,holdenk/spark,chuckchen/spark,wangyum/spark,dongjoon-hyun/spark,ueshin/apache-spark,nchammas/spark,maropu/spark,wangmiao1981/spark,maropu/spark,zero323/spark,milliman/spark,wangyum/spark,vinodkc/spark,nchammas/spark,milliman/spark,gengliangwang/spark,holdenk/spark,witgo/spark,JoshRosen/spark,wangmiao1981/spark,jiangxb1987/spark,rednaxelafx/apache-spark,dongjoon-hyun/spark,zero323/spark,WeichenXu123/spark,taroplus/spark,JoshRosen/spark,xuanyuanking/spark,gengliangwang/spark,srowen/spark,wangmiao1981/spark,WeichenXu123/spark,ueshin/apache-spark,taroplus/spark,witgo/spark,witgo/spark,nchammas/spark,dongjoon-hyun/spark,chuckchen/spark,HyukjinKwon/spark,JoshRosen/spark,wangyum/spark,ueshin/apache-spark,srowen/spark,xuanyuanking/spark,zero323/spark,wangmiao1981/spark,vinodkc/spark,WeichenXu123/spark,srowen/spark,dongjoon-hyun/spark,holdenk/spark,milliman/spark,milliman/spark,zero323/spark,zzcclp/spark,shaneknapp/spark,wangyum/spark,wangmiao1981/spark,cloud-fan/spark