[llvm] [MC] Remove unused includes (NFC) (PR #141321)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `amdgpu-offload-ubuntu-22-cmake-build-only` running on `rocm-docker-ubu-22` while building `llvm` at step 2 "update-annotated-scripts".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/203/builds/11511

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 2 (update-annotated-scripts) failure: update (failure)

```

</details>

https://github.com/llvm/llvm-project/pull/141321