fix: Bump frontend-maven-plugin for Mac M1 builds

[barbeau]

Summary:

As mentioned by @lionel-nj in https://github.com/MobilityData/gtfs-realtime-validator/issues/101, builds currently fail on an Apple Mac M1 due to an issue with the frontend-maven-plugin dependency - see https://github.com/eirslett/frontend-maven-plugin/issues/952#issuecomment-762163294.

As suggested in https://github.com/MobilityData/gtfs-realtime-validator/issues/101, this bumps the version of frontend-maven-plugin so it should build on Mac M1s now.

Closes https://github.com/MobilityData/gtfs-realtime-validator/issues/101.

Expected behavior:

Build on Mac M1s (and all other platforms).

Please make sure these boxes are checked before submitting your pull request - thanks!

• [x] Run the unit tests with mvn test to make sure you didn't break anything
• [x] Format the title like "feat: {new feature short description}" or "fix: {describe what was fixed}". Title must follow the Conventional Commit Specification (https://www.conventionalcommits.org/en/v1.0.0/).
• [x] Linked all relevant issues
• [x] Include screenshot(s) showing how this pull request works and fixes the issue(s)

[isabelle-dr]

After testing on my computer, here are the results:

Master branch:

Branch from this PR:

This seems to be fixing one part of the issue, but we still have the tests failing. I'm merging this PR and will now see if the change in #106 allows me to build the project with a Mac M1.