[ci] unpin CMake version for CUDA + Clang toolchain

[StrikerRUS]

This reverts commit ab474dc.

Refer to #4104.
Closed #4106.

[jameslamb]

This and other PRs are failing due to a Dockerhub outage

https://status.docker.com/pages/history/533c6539221ae15e3f000031

As of a few hours ago:

[Identified] The Docker Hub Registry is returning 503 responses. The cause has been identified and a fix is in progress.

So I think it should be back up again soon, if it isn't already.

https://github.com/microsoft/LightGBM/pull/4183/checks?check_run_id=2355483437

 /usr/bin/docker pull rhub/rocker-gcc-san
  Using default tag: latest
  Error response from daemon: received unexpected HTTP status: 503 Service Unavailable
  Warning: Docker pull failed with exit code 1, back off 9.918 seconds before retry.
  /usr/bin/docker pull rhub/rocker-gcc-san
  Using default tag: latest
  Error response from daemon: received unexpected HTTP status: 503 Service Unavailable
  Warning: Docker pull failed with exit code 1, back off 2.05 seconds before retry.
  /usr/bin/docker pull rhub/rocker-gcc-san
  Using default tag: latest
  Error response from daemon: received unexpected HTTP status: 503 Service Unavailable
  Error: Docker pull failed with exit code 1

[jameslamb]

Where did you see that the changes I mentioned in #4106 made it into cmake 3.20.1? I don't see them mentioned in the release notes for CMake: https://cmake.org/cmake/help/latest/release/3.20.html#id2

I believe you that they are, just want to learn if there are other places i should be looking to keep up with CMake.

[jameslamb]

I approve if this passes!

[StrikerRUS]

Where did you see that the changes I mentioned in #4106 made it into cmake 3.20.1?

Indeed, Release notes of CMake include only new features and major bug fixes. Seems they treated our issue as not a major one.

I decided to check new version of CMake according to the following Milestone info:

[github-actions]

This pull request has been automatically locked since there has not been any recent activity since it was closed. To start a new related discussion, open a new issue at https://github.com/microsoft/LightGBM/issues including a reference to this.