Remove 'added an entry to History.md' requirement for PR's [ci skip]

[MSP-Greg]

Description

PR's are currently required to add an entry to History.md.

This adds to the burden of both contributors and maintainers if multiple PR's exist, as merging one often causes a merge conflict in the remaining open PR's.

The repository https://github.com/MSP-Greg/issue-pr-link has files that will generate the History.md text and update the links within it. It require a GitHub token to access the GitHub API, as it pulls information about both issues and pull requests from it.

It checks the labels for PR's ('bug', feature', & 'refactor') and groups PR's in the text output. It also adds issue links created by using 'fixes #2504` or 'closes #2504' in the PR body text (case insensitive). Sample console output of running history_new_release.rb below:

## major.minor.patch / yyyy-mm-dd

* Features
  * Add debug to worker timeout and startup (#2559, #2528)
  * Print warning when running one-worker cluster (#2565, #2534)
  * Don't close systemd activated socket on pumactl restart (#2563, #2504)


─────────────────────────────────────── Commits without labels?
Add some docs and modify warning message re: single worker warning. [ci skip]
JRuby 9.2.16.0 fixes 9.2.15.0's racc issue

### Your checklist for this pull request
- [x] I have reviewed the [guidelines for contributing](../blob/master/CONTRIBUTING.md) to this repository.
- [x] I have added an entry to [History.md](../blob/master/History.md) if this PR fixes a bug or adds a feature. If it doesn't need an entry to HISTORY.md, I have added `[changelog skip]` or `[ci skip]` to the pull request title.
- [ ] I have added (or updated) appropriate tests if this PR fixes a bug or adds a feature.
- [ ] My pull request is 100 lines added/removed or less so that it can be easily reviewed.
- [ ] If this PR doesn't need tests (docs change), I added `[ci skip]` to the title of the PR.
- [ ] If this closes any issues, I have added "Closes `#issue`" to the PR description or my commit messages.
- [ ] I have updated the documentation accordingly.
- [ ] All new and existing tests passed, including Rubocop.

[cjlarose]

Awesome!