clear_packed_ref_cache(): don't protest if the lock is held

The existing callers already check that the lock isn't held just
before calling `clear_packed_ref_cache()`, and in the near future we
want to be able to call this function when the lock is held.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index f27943f..96d92a5 100644
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -133,8 +133,6 @@ static void clear_packed_ref_cache(struct packed_ref_store *refs)
 	if (refs->cache) {
 		struct packed_ref_cache *cache = refs->cache;
 
-		if (is_lock_file_locked(&refs->lock))
-			die("BUG: packed-ref cache cleared while locked");
 		refs->cache = NULL;
 		release_packed_ref_cache(cache);
 	}