git-status.txt: fix minor asciidoc format issue

The list of additional XY values for submodules in short format
isn't formatted consistently with the rest of the document.
Format as list for consistency.

Signed-off-by: Javier Mora <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: cousteaulecommandant

Documentation/git-status.txt

@@ -246,10 +246,9 @@ U           U    unmerged, both modified
 
 Submodules have more state and instead report
 
-		M    the submodule has a different HEAD than
-		     recorded in the index
-		m    the submodule has modified content
-		?    the submodule has untracked files
+* 'M' = the submodule has a different HEAD than recorded in the index
+* 'm' = the submodule has modified content
+* '?' = the submodule has untracked files
 
 since modified content or untracked files in a submodule cannot be added
 via `git add` in the superproject to prepare a commit.