docs: fix or remove dead links

[ump45nose]

Summary

Fixes five dead links in the docs, verified with HTTP checks (all return 404 as of this PR):

File	Dead link	Fix
docs/README.md	openssl.org/docs/man1.1.0/man1/ciphers.html (404)	point to the current docs.openssl.org/3.5/man1/openssl-ciphers/
docs/installation/methods.yml	archlinux.org/packages/community/any/httpie/ (404 — Arch merged community into extra)	point to /packages/extra/any/httpie/
docs/packaging/linux-arch/README.md	same community URL + /flag/ subpage (404)	point to the extra package page
docs/packaging/README.md	github.com/httpie/debian.httpie.io and github.com/httpie/termible/pull/1 (repos deleted)	keep the prose, drop the dead hyperlinks
docs/packaging/linux-debian/README.md	debian.httpie.io repo / workflow / example-PR links (repo deleted)	keep the prose, drop the dead hyperlinks

Related issue

None found.

Testing

• Every replaced URL was curl-verified to return HTTP 200; every removed URL was verified to return 404.
• Markdown/YAML-only change; no code touched.

Disclosure

For the deleted debian.httpie.io and termible repos I chose to unlink rather than delete the instructions, since the surrounding release process may have moved elsewhere — happy to remove those paragraphs entirely if maintainers prefer.