Update XLA docker image to v0.8 (#93041)
Given the context in https://github.com/pytorch/xla/pull/4489, we now have a new XLA Docker image `v0.8`. This should fix the flaky sccache initialization failures with XLA.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/93041
Approved by: https://github.com/malfet
