read_repository scope can be used for API

What does this MR do?

This is a simple UI fix to let user know they can use limited scope tokens for reading files in their CI

UI disagrees with documentation: https://docs.gitlab.com/ee/api/repository_files.html as per our tests it looks the doc is right. Not sure for write_repository, as this is new and not in our prod yet.

Does this MR meet the acceptance criteria?

Conformity

n/a This is really simple "documentation" fix