ci: Remove psycopg direct dependency as extra, move requirements file to offline build dir

[tchughesiv]

What this PR does / why we need it:

Pypi uploads have issue with the psycopg direct dependency as an extra. This PR removes postres-source extra from pyproject.yaml and instead creates a direct dependency requirements file specifically for offline source builds.

Which issue(s) this PR fixes:

Uploading feast-0.48.0-py2.py3-none-any.whl
25l
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25hWARNING  Error during upload. Retry with the --verbose option for more details. 
ERROR    HTTPError: 400 Bad Request from https://upload.pypi.org/legacy/        
         Can't have direct dependency: psycopg@                                 
         git+https://github.com/psycopg/[email protected]#subdirectory=psycopg ;    
         extra == "postgres-source". See                                        
         https://packaging.python.org/specifications/core-metadata for more     
         information.

Misc