do not install cudf in cudf_polars wheel tests

[jameslamb]

Description

Removes unnecessary installation of cudf wheels in wheel testing for cudf_polars.

cudf_polars doesn't depend on cudf, and neither do its tests. However, right now it's downloading cudf during it's wheel tests. I mistakenly introduced that in #16575.

This introduced a race condition that could lead to CI failures whenever the cudf wheels aren't published yet by the time the cudf_polars tests. Because the cudf_polars wheel tests (rightly) do not wait for cudf wheels to be available:

cudf/.github/workflows/pr.yaml

Lines 154 to 155 in 555734d

	wheel-tests-cudf-polars:
	needs: wheel-build-cudf-polars

cudf/.github/workflows/pr.yaml

Lines 145 to 146 in 555734d

	wheel-build-cudf-polars:
	needs: wheel-build-pylibcudf

Noticed this in #16611

[rapids-download-from-s3] Downloading and decompressing s3://rapids-downloads/ci/cudf/pull-request/16611/a6b7eff/cudf_wheel_python_cudf_cu12_py310_x86_64.tar.gz into ./dist
download failed: s3://rapids-downloads/ci/cudf/pull-request/16611/a6b7eff/cudf_wheel_python_cudf_cu12_py310_x86_64.tar.gz to - An error occurred (404) when calling the HeadObject operation: Not Found

(build link)

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[jameslamb]

/merge

[vyasr]

This wasn't your fault. There's some confusion here. The initial version cudf-polars that we will first release does depend on cudf, but that's going to be based on 24.08. In 24.10 we now have a pylibcudf package and that's the only dependency for cudf-polars.

[jameslamb]

Ah ok, thanks for that @vyasr ! I didn't realize that, that's helpful.