Bump version to match PyTorch (#2924)

Summary:
Updating the version to 2.0.0 to match PyTorch core

Pull Request resolved: https://github.com/pytorch/audio/pull/2924

Reviewed By: carolineechen

Differential Revision: D42098238

Pulled By: mthrok

fbshipit-source-id: 19cb290e493293d1db4211f9bfcdcdffa3e96e45

version.txt

-0.14.0a0
+2.0.0a0