Fix typo radis -> redis

Closes #1938

src/redis.c

@@ -387,7 +387,7 @@ void exitFromChild(int retcode) {
 /*====================== Hash table type implementation  ==================== */
 
 /* This is a hash table type that uses the SDS dynamic strings library as
- * keys and radis objects as values (objects can hold SDS strings,
+ * keys and redis objects as values (objects can hold SDS strings,
  * lists, sets). */
 
 void dictVanillaFree(void *privdata, void *val)