Bump Version 2.1 -> 2.2 (#3585)

Summary: Pull Request resolved: https://github.com/pytorch/audio/pull/3585

Reviewed By: atalman

Differential Revision: D48832146

Pulled By: osalpekar

fbshipit-source-id: c36dd79a0c0f407d490a488902207c8066c01383

version.txt

-2.1.0a0
+2.2.0a0