treewide: remove cache.h inclusion due to previous changes

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/combine-diff.c b/combine-diff.c
index f7e9fb5..f8d6196 100644
--- a/combine-diff.c
+++ b/combine-diff.c
@@ -1,4 +1,4 @@
-#include "cache.h"
+#include "git-compat-util.h"
 #include "object-store.h"
 #include "commit.h"
 #include "convert.h"