Temporarily pin gast 0.2.2 to work around autograph issue.
Temporarily pin gast 0.2.2 to work around autograph issue.

Resolves #143

PiperOrigin-RevId: 268237268
Change-Id: Ia17139b063e32ab5448de850bac406d5de2cf13c

deepmind/sonnet,deepmind/sonnet