Revert "pack-objects: Print a message describing the number of threads for packing"

This reverts commit 6c723f5e.
The additional message may be interesting for git developers,
but not useful for the end users, and clutters the output.

builtin-pack-objects.c

@@ -2239,9 +2239,6 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 #ifdef THREADED_DELTA_SEARCH
 	if (!delta_search_threads)	/* --threads=0 means autodetect */
 		delta_search_threads = online_cpus();
-	if (progress)
-		fprintf(stderr, "Using %d pack threads.\n",
-			delta_search_threads);
 #endif
 
 	prepare_packed_git();