Rename GroupProjectsController file

What does this MR do and why?

With the removal of the GroupsController and ProjectsController we can now rename GroupsProjectController controller into a bit better GroupsController

Screenshots or screen recordings

affected page

How to set up and validate locally

• Sign out. Register new user.
• On the welcome page select Just me and Create a new project.
• Submit the form and finish onboarding.
• Validate group/project are created.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #372454 (closed)