fix(lib): mark changes as MODIFIED on 'MM' in `git_prompt_status` (#9552)

In the output of `git status -sb`, 'MM' indicates there are both added and modified changes.
This change marks that case as MODIFIED instead of ADDED.

lib/git.zsh

@@ -170,7 +170,7 @@ function git_prompt_status() {
     '\?\? '     'UNTRACKED'
     'A  '       'ADDED'
     'M  '       'ADDED'
-    'MM '       'ADDED'
+    'MM '       'MODIFIED'
     ' M '       'MODIFIED'
     'AM '       'MODIFIED'
     ' T '       'MODIFIED'