CI: Avoid manual lookup of the run ID in the release workflow

[leofang]

Currently we require the human operator to fill in both information (git tag and run ID):

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

Lines 22 to 29 in 1137e15

	git-tag:
	description: "The release git tag"
	required: true
	type: string
	run-id:
	description: "The GHA run ID that generated validated artifacts"
	required: true
	type: string

but it does not make sense and it was made so only because I did not spend time digging a solution. Each run ID has a 1:1 relation to the corresponding git commit, and a git tag is just a named git commit. So it should be enough for the operator to provide the git tag alone, and we automatically look up the corresponding run ID.