Brings back original VAD parameters naming

[Purfview]

For no reason in v1.1.0 VAD parameter threshold was changed to onset and neg_threshold to offset.

This PR brings original naming back.

[MahmoudAshraf97]

That is more inline with original silero naming

[MahmoudAshraf97]

As for the failing CI, tokenizers dropped support for python 3.8 in the latest release but due to their wheel structure it will still be installed if you have 3.8, would you suggest adding a requirement to constraint the version or should we drop python 3.8 support and switch CI to 3.9? There is nothing to drop essentially, but we will not be maintaining the requirements that will support 3.8 out of the box. The reason I'm inclined to the second option is that tokenizers is a widely used library and sooner or later faster whisper will start to clash with other projects that require a higher version than what faster whisper needs.
Python 3.8 is EOL since the last month btw.

[Purfview]

That is more inline with original silero naming

What's more important that it's inline with pre-1.1.0 faster-whisper, renaming parameters breaks many projects for no reason.

As for the failing CI, tokenizers dropped support for python 3.8 in the latest release...

Just switch CI to 3.9 I think, anyway, savvy users will be able to solve compatibility issues, I doubt that newbies use 3.8. :)