chore(beep boop 🤖): Bump `MCORE_TAG=31a29b8...` (2024-11-30)
🚀 PR to bump `NVIDIA/Megatron-LM` in `Dockerfile.ci` to `MCORE_TAG=31a29b87cf25f28d524e313de197a8359d2d6789`.  

📝 Please remember the following to-do's before merge: 
- [ ] Verify the presubmit CI  

🙏 Please merge this PR only if the CI workflow completed successfully.