Remove redundant step in CodeQL GitHub Actions step (#14600)
Remove redundant step in CodeQL GitHub Actions step (#14600)

From https://github.com/apache/airflow/runs/2031451066#step:4:9

Warning: 1 issue was detected with this workflow: git checkout HEAD^2 is no longer necessary.
Please remove this step as Code Scanning recommends analyzing the merge commit for best results.

I also double-check it with https://github.com/github/codeql-action
cfei18/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,apache/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,sekikn/incubator-airflow,apache/incubator-airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,apache/incubator-airflow,cfei18/incubator-airflow,apache/airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,sekikn/incubator-airflow,bolkedebruin/airflow,dhuang/incubator-airflow,apache/airflow,danielvdende/incubator-airflow,dhuang/incubator-airflow,bolkedebruin/airflow,sekikn/incubator-airflow,nathanielvarona/airflow,nathanielvarona/airflow,mistercrunch/airflow,sekikn/incubator-airflow,Acehaidrey/incubator-airflow,mistercrunch/airflow,nathanielvarona/airflow,dhuang/incubator-airflow,bolkedebruin/airflow,apache/airflow,nathanielvarona/airflow,mistercrunch/airflow,lyft/incubator-airflow,Acehaidrey/incubator-airflow,bolkedebruin/airflow,apache/airflow,apache/airflow,bolkedebruin/airflow,Acehaidrey/incubator-airflow,nathanielvarona/airflow,mistercrunch/airflow,cfei18/incubator-airflow,apache/incubator-airflow,dhuang/incubator-airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,lyft/incubator-airflow,cfei18/incubator-airflow,lyft/incubator-airflow,nathanielvarona/airflow,cfei18/incubator-airflow