Add postgres/ to .gitignore

`docker-compose.yml` contains a volume mapping from  `./postgres` to `/var/lib/postgresql/data`, which creates a "postgres" directory that needs to be ignored by version control.
1 job for gitignore-postgres
Status Name Job ID Coverage
failed test #5700

Name Stage Failure
test Test There has been a timeout failure or the job got stuck. Check your timeout limits or try again
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