[examples/language/roberta] remove redundant texts & update roberta

[mandoxzhang]

📝 What does this PR do?

In pull request from ， the PR brings redundant conflict text from examples/language/roberta/pretraining/run_pretraining.py, such as "<<<<<<< HEAD". In this PR, I remove the redundant texts above.

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• I have performed a self-review of my code
• I have added thorough tests.
• I have added docstrings for all the functions/methods I implemented

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