Cluster: some zunionInterGetKeys() comment trimmed.

Everything was pretty clear again from the initial statements.

src/db.c

@@ -995,19 +995,14 @@ int *zunionInterGetKeys(struct redisCommand *cmd,robj **argv, int argc, int *num
     }
 
     /* Keys in z{union,inter}store come from two places:
-       argv[1] = storage key,
-       argv[3...n] = keys to intersect */
-
-    /* (num+1) is (argv[2] + 1) to account for argv[1] too */
+     * argv[1] = storage key,
+     * argv[3...n] = keys to intersect */
     keys = zmalloc(sizeof(int)*(num+1));
 
     /* Add all key positions for argv[3...n] to keys[] */
     for (i = 0; i < num; i++) keys[i] = 3+i;
 
-    /* Now add the argv[1] key position (the storage key target)
-       to our list of command positions containing keys.
-       num is the number of source keys, but we initialized
-       keys[] to size num+1, so keys[num] is safe and valid and okay. */
+    /* Finally add the argv[1] key position (the storage key target). */
     keys[num] = 1;
     *numkeys = num+1;  /* Total keys = {union,inter} keys + storage key */
     return keys;