Gmail Rego: Remove Log Event Implementation

[rlxdev]

🗣 Description

Removed the older log event implementation for most of the Gmail baselines now that Google's Policy API has been released.

Log event code in gmail.rego was removed, and the corresponding test files have been deleted:

gmail01_test.rego
gmail05_test.rego
gmail06_test.rego
gmail07_test.rego
gmail08_test.rego
gmail09_test.rego
gmail11_test.rego
gmail12_test.rego
gmail14_test.rego

The following files were modified to remove tests no longer needed, leaving tests for baselines that still rely on log events.

gmail10_test.rego
gmail15_test.rego

Closes #507

🧪 Testing

Ran Rego checks.
Ran ScubaGoggles to make sure it's running correctly.

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• If applicable, All future TODOs are captured in issues, which are referenced in the PR description.
• The relevant issues PR resolves are linked preferably via closing keywords.
• All relevant type-of-change labels have been added.
• I have read and agree to the CONTRIBUTING.md document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

✅ Pre-merge Checklist

• This PR has been smoke tested to ensure main is in a functional state when this PR is merged.
• Squash all commits into one PR level commit using the Squash and merge button.

✅ Post-merge Checklist

• Delete the branch to clean up.
• Close issues resolved by this PR if the closing keywords did not activate.