Make comment name match var name in activeExpireCycle().

src/redis.c

@@ -713,7 +713,7 @@ void activeExpireCycle(void) {
              * expire. So after a given amount of milliseconds return to the
              * caller waiting for the other active expire cycle. */
             iteration++;
-            if ((iteration & 0xf) == 0 && /* check once every 16 cycles. */
+            if ((iteration & 0xf) == 0 && /* check once every 16 iterations. */
                 (ustime()-start) > timelimit) return;
         } while (expired > REDIS_EXPIRELOOKUPS_PER_CRON/4);
     }