treewide: remove cache.h inclusion due to object-name.h changes

Signed-off-by: Elijah Newren <newren@gmail.com>
Acked-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/mailmap.c b/mailmap.c
index d62d7bf..28d389c 100644
--- a/mailmap.c
+++ b/mailmap.c
@@ -1,4 +1,4 @@
-#include "cache.h"
+#include "git-compat-util.h"
 #include "environment.h"
 #include "string-list.h"
 #include "mailmap.h"