Remove useless casts to (void *) in hash_search() calls

Some of these appear to be leftovers from when hash_search() took a
char * argument (changed in 5999e78fc4).

Since after this there is some more horizontal space available, do
some light reformatting where suitable.

Reviewed-by: Corey Huinker <corey.huinker@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/fd9adf5d-b1aa-e82f-e4c7-263c30145807%40enterprisedb.com

src/backend/optimizer/util/predtest.c

@@ -2040,7 +2040,7 @@ lookup_proof_cache(Oid pred_op, Oid clause_op, bool refute_it)
 	key.pred_op = pred_op;
 	key.clause_op = clause_op;
 	cache_entry = (OprProofCacheEntry *) hash_search(OprProofCacheHash,
-													 (void *) &key,
+													 &key,
 													 HASH_ENTER, &cfound);
 	if (!cfound)
 	{