[Dev] Remove duplicated bias_act_func from main to dev sync

[yaox12]

• I, the PR author, have personally reviewed every line of this PR.

What does this PR do ?

This should be some garbage from main to dev sync.

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[yaox12]

/ok to test c39e735

[svcnvidia-nemo-ci]

🔄 Merge queue validation started!

You can track the progress here: https://github.com/NVIDIA/Megatron-LM/actions/runs/26277240990