treewide: remove cache.h inclusion due to environment.h changes

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/prompt.c b/prompt.c
index ba10813..3baa33f 100644
--- a/prompt.c
+++ b/prompt.c
@@ -1,4 +1,4 @@
-#include "cache.h"
+#include "git-compat-util.h"
 #include "config.h"
 #include "environment.h"
 #include "run-command.h"