GH-103484: Fix broken links reported by linkcheck (#103608)

* Doc: Fix broken links reported by linkcheck

* Apply suggestions from code review

- Remove extra diff line in faq/library.rst (merwok)
- Use HTTPS to link Unicode 15.0.0 to solve a redirect (hugovk)
- Use wayback machine link for openssl 1.1.0 instead of linking 1.1.1, "as this text mentions a feature from 1.1.0" (hugovk)

Co-authored-by: Éric <merwok@netwok.org>
Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>

* Doc: Make mark-up code as literal

* Doc: Alphabetize items in linkcheck_ignore

Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>

* Doc: Improve comment in sphinx conf

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>

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Co-authored-by: Éric <merwok@netwok.org>
Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>