UI issue with branch name from issue form

What does this MR do and why?

• Main fix: add invalid character support to a new branch from the issues dropdown. Which caused errors when we tried to create the branch.
• Quick fix: typo in the app/controllers/projects/branches_controller.rb - fixed in Fix typo in the error message rendering (!113027 - merged)

See discussion here for !93108 (comment 1145764394) for more context

Screenshots or screen recordings

Before	After
720-branch-name-no-checks	720-branch-name-with-checks

Related issues:

• #21243 (closed)
• #379083 (closed)