Unnecessary suggestion to fork when editing file on commit tree

Steps to reproduce

• navigate to project that you are member of
• open tree/repository view of a commit
• click edit button

What is the current bug behavior?

suggestion to fork the project:

What is the expected correct behavior?

either edit button is not displayed or error message is shown that files cannot be edited in commit tree

even better would be #21963

Plan

Disable the Edit button with a tooltip explaining we can't edit a file in the commit view