CI: Make `build-ctk-ver` in the release workflow optional (or just drop it)

[leofang]

Currently, we require build-ctk-ver as an input to the release workflow

cuda-python/.github/workflows/release.yml

Lines 31 to 33 in 36b8c5f

	build-ctk-ver:
	type: string
	required: true

because we need to pass it to the doc build step:

cuda-python/.github/workflows/release.yml

Lines 123 to 125 in 36b8c5f

	uses: ./.github/workflows/build-docs.yml
	with:
	build-ctk-ver: ${{ inputs.build-ctk-ver }}

However, I think this is unnecessary now that we resolved #326 and #327. That is, this WAR can be removed now:

cuda-python/.github/workflows/build-docs.yml

Lines 74 to 79 in 36b8c5f

	# WAR: Building the doc currently requires CTK installed (NVIDIA/cuda-python#326,327)
	- name: Set up mini CTK
	uses: ./.github/actions/fetch_ctk
	with:
	host-platform: linux-64
	cuda-version: ${{ inputs.build-ctk-ver }}

We still need to figure out how to get the artifact that is based on build-ctk-ver there:

cuda-python/.github/workflows/build-docs.yml

Line 100 in 36b8c5f

CUDA_BINDINGS_ARTIFACT_BASENAME="cuda-bindings-python${PYTHON_VERSION_FORMATTED}-cuda${{ inputs.build-ctk-ver }}-linux-64"

But I am hopeful that this bit can be automated so that the workflow user does not need to type anything.

[cpcloud]

Done in #1751.