audit: Fix Regexp for stripping .git from repo URLs

- [For a formula named
  turbogit](https://github.com/Homebrew/homebrew-core/pull/55208), we
  didn't see any of the notability checks fail CI.
- The repo name was getting truncated to `turb`, which didn't exist, so
  the audit didn't return anything for this check.
- The Regexp to strip `.git` from the end of was not escaping the `.`,
  so it would match anything ending in `git`, not a literal `.git`.

Library/Homebrew/dev-cmd/audit.rb

@@ -597,7 +597,7 @@ module Homebrew
       _, user, repo = *regex.match(formula.homepage) unless user
       return if !user || !repo
 
-      repo.gsub!(/.git$/, "")
+      repo.delete_suffix!(".git")
 
       [user, repo]
     end