diff --color-moved-ws: fix another memory leak

This is obvious in retrospect, it was found with asan.
Signed-off-by: NPhillip Wood <phillip.wood@dunelm.org.uk>
Reviewed-by: NStefan Beller <sbeller@google.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

diff.c

@@ -994,6 +994,8 @@ static void pmb_advance_or_null_multi_match(struct diff_options *o,
 			moved_block_clear(&pmb[i]);
 		}
 	}
+
+	free(got_match);
 }
 
 static int shrink_potential_moved_blocks(struct moved_block *pmb,