Clean up PyTorch FA tests

[Micky774]

Description

Removes the use of share_cu_seqlens_ref to target a specific code-path in our AITER/CK FA workflow.

Fixes # (issue)

Type of change

• Documentation change (change only to the documentation, either a fix or a new content)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Infra/Build change
• Code refactoring

Changes

Please list the changes introduced in this PR:

• Change A
• Change B

Checklist:

• I have read and followed the contributing guidelines
• The functionality is complete
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[wangye805]

LGTM.

By the way, did you compare with NVTE upstream source codes to see the code diff in case we miss some previously edited places? Thanks

[Micky774]

LGTM.

By the way, did you compare with NVTE upstream source codes to see the code diff in case we miss some previously edited places? Thanks

I've checked and just pushed a commit which will minimize the diff wrt upstream