Use childNodes[2] for finding file resolution

I was getting a ton of post parsing errors with the latest version of 4chan X, and after a bit of digging I managed to figure out the reason. ExLinks support vanilla 4chan and can add in its reverse image search link to the .fileText before 4chan X manages to parse it. As a result, 4chan X ends up looking at the ExLinks-added reverse image search link for dimensions instead of the correct text element. Using childNodes[2] instead of lastChild should fix this.