Revert "Fixed typo in SCAN comment. iff -> if."

Probably here Pieter means "if and only if".

This reverts commit 43fdf3b404413f6e3b2c39ac491238c70ecee81c.

src/db.c

@@ -352,7 +352,7 @@ void scanCommand(redisClient *c) {
             pat = c->argv[i+1]->ptr;
             patlen = sdslen(pat);
 
-            /* The pattern is a no-op if == "*" */
+            /* The pattern is a no-op iff == "*" */
             patnoop = (pat[0] == '*' && patlen == 1);
 
             i += 2;