Check references to master

[rtyley]

The master branch of this repository has been migrated to main using the master-to-main tool.

Some files in the repository contain the word master. Please check the following files and update where required:

• [ ] test/lib/GitChangesSpec.scala
• [ ] test/FunctionalSpec.scala
• [ ] test/lib/ConfigFinderSpec.scala
• [ ] app/lib/RepoSnapshot.scala
• [ ] notes.md
• [ ] test/lib/Helpers.scala
• [ ] artwork/prout-pull-request-history-diagram.svg