Remove setting of PT_HPU_LAZY_MODE=2 in training_args.py

[vivekgoe]

What does this PR do?

Cleanup code in training_args.py to remove setting of PT_HPU_LAZY_MODE=2 (this is not supported SynapseAI release 1.13.0 onwards).

Fixes # (issue)

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

[HuggingFaceDocBuilderDev]

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[vivekgoe]

@regisss Since I pushed this PR from a fork which has a different name "HabanaAI/optimum-habana-fork" instead of usual "user-name/optimum-habana , there was a failure in Build PR documentation step. I added a small change to Dockerfile to fix this.
With change in this PR, only eager mode test we have (test_trainer.py/test_eager_mode) started failing (throwing new assert we have added in this PR). This can be fixed only when whole test suite is switched to PT_HPU_LAZY_MODE=0, reason is that this environment variable can't be updated once Synapse SW is loaded. For now I have added a skip for this test, please suggest if you can think of a better solution.

[regisss]

LGTM