Remove pkg/ from .gitignore

[acrmp]

Description

• This was causing linting failures due to subdirectories of vendored modules being ignored.
• I think the .gitignore entry dates from when this repo set itself as the GOPATH and Go would generate files to that directory.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Testing performed?

• Unit tests
• Integration tests
• Acceptance tests

Checklist:

• This PR is being made against the main branch, or relevant version branch
• I have made corresponding changes to the documentation
• I have added testing for my changes

If you have any questions, or want to get attention for a PR or issue please reach out on the #logging-and-metrics channel in the cloudfoundry slack

[ctlong]

It looks like the tests and linting are still failing?

[acrmp]

I'd planned on having our tooling commit the missing files once the exclusion was removed but have now pushed a second commit with the previously excluded files.