Simplify comment

src/subscribe.c

@@ -169,11 +169,7 @@ void prune_dead_subscribers(void)
 	subscriber_list_t *sb = subscribe_head;
 	while (sb != NULL) {
 		subscriber_list_t *next = sb->next;
-		// To check if a subscriber's stream is still open and writable call
-		// write with an empty buffer and check the returned value. If the
-		// stream is not writable anymore (i.e. it has been closed because the
-		// process associated to this subscriber no longer exists) then write()
-		// will return -1.
+		// Is the subscriber's stream closed?
 		if (write(fileno(sb->stream), NULL, 0) == -1) {
 			remove_subscriber(sb);
 		}