Run changelog-check only on PR context (@W-16164410@)

[adamraya]

Description

PR follow up of https://github.com/SalesforceCommerceCloud/pwa-kit/pull/1948 that simplifies the GA changelog check to only run in the PR context. It also uses the values available in GA without the need to use the API calls.

Types of Changes

• [ ] Bug fix (non-breaking change that fixes an issue)
• [ ] New feature (non-breaking change that adds functionality)
• [ ] Documentation update
• [ ] Breaking change (could cause existing functionality to not work as expected)
• [ ] Other changes (non-breaking changes that does not fit any of the above)

Breaking changes include:

• Removing a public function or component or prop
• Adding a required argument to a function
• Changing the data type of a function parameter or return value
• Adding a new peer dependency to package.json

Changes

• Updated changelog-check to only run on PR context

How to Test-Drive This PR

Check the GA builds for the tested scenarios:

1. PASS Test Commit with changes on non-public packages: https://github.com/SalesforceCommerceCloud/pwa-kit/pull/2006/commits/7bd1d2364de79415a27ee951832bb40d54da49d0

2. PASS Test Commit without updating the Changelog.md file and the skip changelog label: https://github.com/SalesforceCommerceCloud/pwa-kit/pull/2006/commits/af131f09b8b9b98bab53ec628a2e57b853c02063

3. FAIL Test Commit without updating the Changelog.md file: https://github.com/SalesforceCommerceCloud/pwa-kit/pull/2006/commits/7fecf148a49d245bafa71c5565b6bb85ca99ea53

• Feel free to branch off ga-check-changelog-only-on-pr base branch and create your own PR for further testing.

Checklists

General

• [ ] Changes are covered by test cases
• [ ] CHANGELOG.md updated with a short description of changes (not required for documentation updates)

Accessibility Compliance

You must check off all items in one of the follow two lists:

• [ ] There are no changes to UI

or...

• [ ] Changes were tested with a Screen Reader (iOS VoiceOver or Android Talkback) and had no issues
• [ ] Changes comply with WCAG 2.0 guidelines levels A and AA
• [ ] Changes to common UI patterns and interactions comply with WAI-ARIA best practices

Localization

• [ ] Changes include a UI text update in the Retail React App (which requires translation)