[YT] Fix incorrect format code descriptions

Corrects the descriptions for the DASH video format codes 264 and 138
(1440p and 2160p, respectively). I see no reason for the values to be what they are currently are, and this problem is mentioned in issue #2400, so this should fix that,

This is my first pull request, and I don't really understand git, so if I'm doing something wrong, feel free to tell me.