ReturnYouTubeDislike - handle if YouTube video owner set video likes to hidden

[LisoUseInAIKyrios]

RYD API does not collect or provide data for videos where the creator has enabled hiding the like count.

Example video: https://www.youtube.com/watch?v=UnrU5vxCHxw
RYD data: https://returnyoutubedislikeapi.com/votes?videoId=UnrU5vxCHxw

As per: Anarios/return-youtube-dislike#530
Do not show a dislike count for these type of videos, as no dislike data is available.

Other code changes include:

• use HTTP request headers as specified by RYD API
• added a thread pool executor (video UI seems to load a little faster since UI does not wait for a resource heavy thread to create and start)
• simplified ReturnYouTubdeDislike fetch code using a Future object
• removing the non-functional interrupt logic (If the calling thread is interrupted, HttpURLConnection continues to run and does not halt or throw an exception). Interrupting is not needed anyways since the timeout is so short.
• voting runs on a single thread executor (removes the need to synchronize voting/registration)
• reduced UI blocking timeout to 4 seconds (with 5 seconds it could still trigger an Android "App Not Responding" message)

I've been using this for a few days and it's working well for me.