feat: Update references to Dataset Publishing Guidelines from #1601

[emmambd]

Summary:

Dataset Publishing Guidelines and All Files Recommendations were moved from the best practices section of the spec to the reference file, and as referenced in #1601. This PR updates the links to the References sections of the corresponding rules so no links break.

Expected behavior:

mixed_case_recommended_field
expired_calendar

both link to https://gtfs.org/schedule/reference/.

[github-actions]

This contribution does not follow the conventions set by the Google Java style guide. Please run the following command line at the root of the project to fix formatting errors: ./gradlew goJF.

[github-actions]

This contribution does not follow the conventions set by the Google Java style guide. Please run the following command line at the root of the project to fix formatting errors: ./gradlew goJF.

[github-actions]

✅ Rule acceptance tests passed.
New Errors: 0 out of 1477 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
Dropped Errors: 0 out of 1477 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
New Warnings: 0 out of 1477 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
Dropped Warnings: 0 out of 1477 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
0 out of 1477 sources (~0 %) are corrupted.
Commit: 799b444
Download the full acceptance test report here (report will disappear after 90 days).
✅ Rule acceptance tests passed.

[github-actions]

✅ Rule acceptance tests passed.
New Errors: 0 out of 1477 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
Dropped Errors: 0 out of 1477 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
New Warnings: 0 out of 1477 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
Dropped Warnings: 0 out of 1477 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
0 out of 1477 sources (~0 %) are corrupted.
Commit: 3b8fafc
Download the full acceptance test report here (report will disappear after 90 days).
✅ Rule acceptance tests passed.

[davidgamez]

LGTM