remove some unnecessary libcudf nightly builds

[jameslamb]

Description

Follow-up to #16650 and #15483.

libcudf wheels are identical (same content, same filename) across Python versions, but due to an oversight in the PRs linked above, we're currently building nightlies of them once per Python version supported by RAPIDS 😭

You can see this on recent runs of the build workflow:

(build link)

This PR fixes that by applying the same matrix filter to libcudf nightly build jobs as is currently applied to PR jobs:

cudf/.github/workflows/pr.yaml

Lines 195 to 200 in 5e420ff

	wheel-build-libcudf:
	needs: checks
	secrets: inherit
	uses: rapidsai/shared-workflows/.github/workflows/[email protected]
	with:
	matrix_filter: group_by([.ARCH, (.CUDA_VER|split(".")|map(tonumber)|.[0])]) | map(max_by(.PY_VER|split(".")|map(tonumber)))

Checklist

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

[bdice]

/merge