Documentation/git-mv.txt: fix whitespace indentation

Replace spaces with tabs to avoid a warning when further patches change
these lines.

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-mv.txt

@@ -32,10 +32,10 @@ OPTIONS
 --force::
 	Force renaming or moving of a file even if the target exists
 -k::
-        Skip move or rename actions which would lead to an error
+	Skip move or rename actions which would lead to an error
 	condition. An error happens when a source is neither existing nor
 	controlled by Git, or when it would overwrite an existing
-        file unless '-f' is given.
+	file unless '-f' is given.
 -n::
 --dry-run::
 	Do nothing; only show what would happen