Rename master to main for all three Validation GitHub repositories

I request renaming the master branch to main on the following three repositories. For convenience, I'll use the existing issues in the corresponding issue trackers.

• Rename master to main · Issue #187 · jakartaee/validation (github.com)
• Rename master to main · Issue #193 · jakartaee/validation-tck (github.com)
• Rename master to main · Issue #272 · jakartaee/validation-spec (github.com)