Upgrade to pr-bumper@2.x

[job13er]

This project uses semver, please check the scope of this pr:

• [ ] #none# - documentation fixes and/or test additions
• [x] #patch# - backwards-compatible bug fix
• [ ] #minor# - adding functionality in a backwards-compatible manner
• [ ] #major# - incompatible API change

This isn't really a patch, but want to make sure publishing still works with the new pr-bumper, so calling it a patch.

CHANGELOG

• Upgraded pr-bumper to support pre-releases so we can create a 8.0-beta branch.

[coveralls]

Changes Unknown when pulling 02752eca0e5baf2a406fd75c82f37b60509cca1f on job13er:upgrade-pr-bumper into on ciena-frost:master.

[job13er]

Approved