fix: update thumbnail dot selectors to target button-view-model

[Pallavi-p-h]

Fixes #3822

Added CSS rules targeting the new <button-view-model> element to hide the thumbnail menu. Legacy selectors were kept as fallbacks.

[ImprovedTube2]

Thank you! @Pallavi-p-h
Please don't change formatting(, for now. It's embarrassing GitHub doesn't allow to undo this automatically yet, and so we may (near the top of our to-do list) add and/or make a GitHub action for it)

Kept the legacy selectors intact as fallbacks for users who might still be served older cached versions of the YouTube UI.

That's what we might do at any doubt, including the date in a comment.

LLM summaries lie.
Disclosure is advised. (And brevity for maintainers, such as an empty description field)
You don't have to take the risk of random words appearing in your name.

How to Test

(you can say untested at any doubt.)
(and/or refine or extend our wiki / introductions)

[Pallavi-p-h]

@ImprovedTube2 Thanks for the review and tips. I have amended the PR to remove the unintended formatting changes. I also added the legacy selectors back as fallbacks (with a date comment) and shortened the PR description.

[ImprovedTube2]

Thank you so much! @Pallavi-p-h