Synchronize submodules with LLVM at llvm/llvm-project@955b91c19c00

Updates LLVM dependencies to match
[955b91c19c00](https://github.com/llvm/llvm-project/commit/955b91c19c00).
- TensorFlow to
[c74a7b01697e](https://github.com/tensorflow/tensorflow/commit/c74a7b01697e)
- MLIR-HLO to
[8ccf8556ad84](https://github.com/tensorflow/mlir-hlo/commit/${MLIR_HLO_SHA?})

`./scripts/git/update_to_llvm_syncpoint.py`

Automated submodule bump from .github/workflows/update_llvm_dependent_submodules.yml

PiperOrigin-RevId: 392491605