Addresses requested changes for Leetcode Solution 305

Replaces <   with   &lt; 
Replaces O(k log(mn))   with   $O(k log(mn))$
where asked to do so.

Author: SanskarSinghiit

dsa-solutions/lc-solutions/0300-0399/0305-number-of-islands-ii.md

@@ -47,7 +47,7 @@ Output: [1]
 - 0 <= ci < n
 
 ### Follow up
-Could you solve it in time complexity O(k log(mn)), where k == positions.length?
+Could you solve it in time complexity $O(k log(mn))$, where k == positions.length?
 
 ## Solution