Fix: Kind attribute missing subtitle value in video text track

[sunnyssr]

Description

In video text track, kind attribute takes any value in Gutenberg editor.
When the block is rendered, it shows the selected kind attribute. But in case of subtitles, same doesn't happen. It doesn't show the kind attribute.

How has this been tested?

Screenshots

Before:

After:

Types of changes

fixes #26673

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR.

cc @annezazu @paaljoachim

[gwwar]

Thanks @sunnyssr this one tests well for me!

The one difference in behavior is that if this block switches it's default kind in the future, existing blocks won't use that default. I think this is fine, since most folks wouldn't expect that to change, if say they added a video track, published, and a future wp or plugin update changed their defaults.

cc @jorgefilipecosta in case I missed some other usecase.