tree-diff: show_path prototype is not needed anymore

We moved all action-taking code below show_path() in recent HEAD~~
(tree-diff: move all action-taking code out of compare_tree_entry).
Signed-off-by: NKirill Smelkov <kirr@mns.spb.ru>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

tree-diff.c

@@ -6,9 +6,6 @@
 #include "diffcore.h"
 #include "tree.h"
 
-static void show_path(struct strbuf *base, struct diff_options *opt,
-		      struct tree_desc *t1, struct tree_desc *t2);
-
 /*
  * Compare two tree entries, taking into account only path/S_ISDIR(mode),
  * but not their sha1's.