Check references to master

[markjamesbutler]

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:

• README.md
• people-repo.md
• app/lib/PeopleRepo.scala
• app/views/userPages/index.scala.html
• heroku.md
• app/lib/AccountRequirement.scala