Replace dictionary creation with dictionary literal (#13474)
Replace dictionary creation with dictionary literal (#13474)

Instead of:

```
ctx = {}
ctx['filename'] = filename
```

we can use:

```
ctx = {'filename': filename}
```
nathanielvarona/airflow,Acehaidrey/incubator-airflow,nathanielvarona/airflow,bolkedebruin/airflow,apache/incubator-airflow,cfei18/incubator-airflow,lyft/incubator-airflow,apache/airflow,bolkedebruin/airflow,apache/airflow,sekikn/incubator-airflow,cfei18/incubator-airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,apache/airflow,bolkedebruin/airflow,dhuang/incubator-airflow,nathanielvarona/airflow,lyft/incubator-airflow,sekikn/incubator-airflow,bolkedebruin/airflow,dhuang/incubator-airflow,mistercrunch/airflow,apache/airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,Acehaidrey/incubator-airflow,Acehaidrey/incubator-airflow,apache/incubator-airflow,cfei18/incubator-airflow,mistercrunch/airflow,danielvdende/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,danielvdende/incubator-airflow,sekikn/incubator-airflow,mistercrunch/airflow,Acehaidrey/incubator-airflow,apache/incubator-airflow,danielvdende/incubator-airflow,lyft/incubator-airflow,dhuang/incubator-airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,mistercrunch/airflow,Acehaidrey/incubator-airflow,bolkedebruin/airflow,cfei18/incubator-airflow,nathanielvarona/airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,apache/incubator-airflow,sekikn/incubator-airflow,dhuang/incubator-airflow