[llvm] [AMDGPU][GISel] Clean trailing Imms from RegBankLegalize rules. NFC (PR #204195)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `openmp-s390x-linux` running on `systemz-1` while building `llvm` at step 2 "checkout".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/88/builds/23744

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

```
Step 2 (checkout) failure: update (failure)
git version 2.34.1
remote: This request was rate-limited due to too many requests from your network. Reduce the frequency of your requests or try again later.
remote: For more on scraping GitHub and how it may affect your rights, please review our Terms of Service (https://docs.github.com/en/site-policy/github-terms/github-terms-of-service).
fatal: unable to access 'https://github.com/llvm/llvm-project.git/': The requested URL returned error: 429
remote: This request was rate-limited due to too many requests from your network. Reduce the frequency of your requests or try again later.
remote: For more on scraping GitHub and how it may affect your rights, please review our Terms of Service (https://docs.github.com/en/site-policy/github-terms/github-terms-of-service).
fatal: unable to access 'https://github.com/llvm/llvm-project.git/': The requested URL returned error: 429

```

</details>

https://github.com/llvm/llvm-project/pull/204195