FIX-#6974: Always use actual pandas version in 'test_all_urls_exist'

[dchigarev]

What do these changes do?

The PR starts using PANDAS_API_URL_TEMPLATE that always contains an actual pandas version instead of raw urls (if the pandas version in the url doesn't match with the installed one, the test fails)

• first commit message and PR title follow format outlined here

  NOTE: If you edit the PR title to match this format, you need to add another commit (even if it's empty) or amend your last commit for the CI job that checks the PR title to pick up the new PR title.

• passes flake8 modin/ asv_bench/benchmarks scripts/doc_checker.py
• passes black --check modin/ asv_bench/benchmarks scripts/doc_checker.py
• signed commit with git commit -s
• Resolves Fix pandas version in test_all_urls_exist #6974
• tests added and passing
• module layout described at docs/development/architecture.rst is up-to-date

[YarShev]

Suggested change

	for broken_method in methods_with_broken_urls:
	doc_urls.remove(PANDAS_API_URL_TEMPLATE.format(broken_method))
	for broken_url in methods_with_broken_urls:
	doc_urls.remove(PANDAS_API_URL_TEMPLATE.format(broken_url))

[YarShev]

Is it clearer?

[dchigarev]

why? we're iterating over method names here, not urls