git-relink: use a lowercase "usage:" string

Make the usage string consistent with Git.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-relink.perl

@@ -163,7 +163,7 @@ sub link_two_files($$) {
 
 
 sub usage() {
-	print("Usage: git relink [--safe] <dir>... <master_dir> \n");
+	print("usage: git relink [--safe] <dir>... <master_dir> \n");
 	print("All directories should contain a .git/objects/ subdirectory.\n");
 	print("Options\n");
 	print("\t--safe\t" .