Bump 3rdparty/Megatron-LM from 2da43ef to 2d7c521

Bumps [3rdparty/Megatron-LM](https://github.com/NVIDIA/Megatron-LM) from `2da43ef` to `2d7c521`.
- [Release notes](https://github.com/NVIDIA/Megatron-LM/releases)
- [Commits](NVIDIA/Megatron-LM@2da43ef...2d7c521)

---
updated-dependencies:
- dependency-name: 3rdparty/Megatron-LM
  dependency-type: direct:production
...

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