[llvm] [GitHub] Bump clang-tidy version to 21th in CI (PR #160551)

[Baranov Victor via llvm-commits]

================
@@ -19,8 +19,6 @@ jobs:
     defaults:
       run:
         shell: bash
-    container:
----------------
vbvictor wrote:

When setup-cpp [action is run](https://github.com/llvm/llvm-project/actions/runs/17957764639/job/51073582915), it "fails" with such error:
```
Installing setup-cpp at 1.1.1 via npm...
Error: Failed to install the setup-cpp at 1.1.1 CLI: Error: Command failed with ENOENT: npm install -g setup-cpp at 1.1.1
spawn npm ENOENT. Ignoring...
✅ clang-tidy was installed successfully:
```
"fails" is quoted because it `clang-tidy` still is installed in the path.  The only drawback is this annotation in UI:
<img width="2505" height="347" alt="image" src="https://github.com/user-attachments/assets/b20d39c6-9284-4c28-9d99-52d1755aa06c" />

>From logs, it seems there are some problems with `systemd` during installation:
```
  /usr/lib/tmpfiles.d/systemd-network.conf:10: Failed to resolve user 'systemd-network': No such process
  /usr/lib/tmpfiles.d/systemd-network.conf:11: Failed to resolve user 'systemd-network': No such process
  /usr/lib/tmpfiles.d/systemd-network.conf:12: Failed to resolve user 'systemd-network': No such process
  /usr/lib/tmpfiles.d/systemd-network.conf:13: Failed to resolve user 'systemd-network': No such process
  /usr/lib/tmpfiles.d/systemd.conf:22: Failed to resolve group 'systemd-journal': No such process
  /usr/lib/tmpfiles.d/systemd.conf:23: Failed to resolve group 'systemd-journal': No such process
  /usr/lib/tmpfiles.d/systemd.conf:28: Failed to resolve group 'systemd-journal': No such process
  /usr/lib/tmpfiles.d/systemd.conf:29: Failed to resolve group 'systemd-journal': No such process
  /usr/lib/tmpfiles.d/systemd.conf:30: Failed to resolve group 'systemd-journal': No such process
```
This leads to [this](https://askubuntu.com/questions/1511770/error-while-installing-systemd-on-base-ubuntu-24-04-docker-image) topic, but I can't understand how given answer correlate to us because it said "The host was Ubuntu 20.04 and the image was 24.04.", but we run ubuntu-24 docker image on ubuntu-24 runner.

I found that if I remove this container (which is not used in `clang-format`) everything installs correctly, and I didn't see significant downgrade of compilation speed.


https://github.com/llvm/llvm-project/pull/160551