Update megatron-lm package

[loadams]

Megatron-lm on pypi deleted all old versions, including the 1.1.5 that we used to use, though that version didn't correlate with their git tags/releases. They've re-added package 2.2.2 on the pypi feed that has the following description:

This is a placeholder for megatron-lm package v1.1.5

This appears to be not true, although it does seem to roughly correlate with the git tag v2.2 which is where git bisect indicates the release we were using came from. This pacakge doesn't have the contents we would expect, so we cannot use it either.

This PR reverts the skips on tests that would fail when removing the megatron-lm version before as well.