gh-101100: Fix Sphinx warning in library/http.cookies.rst

[hugovk]

Fix these warnings:

❯ SPHINXERRORHANDLING=-n PATH=./venv/bin:$PATH sphinx-build -b html -d build/doctrees -j auto -n . build/html library/http.cookies.rst 2>&1 | grep WARNING | tee >(wc -l)
Doc/library/http.cookies.rst:57: WARNING: py:meth reference target not found: value_decode
Doc/library/http.cookies.rst:57: WARNING: py:meth reference target not found: value_encode
Doc/library/http.cookies.rst:144: WARNING: py:attr reference target not found: httponly
Doc/library/http.cookies.rst:148: WARNING: py:attr reference target not found: samesite
Doc/library/http.cookies.rst:155: WARNING: py:meth reference target not found: Morsel.__eq__
Doc/library/http.cookies.rst:164: WARNING: py:attr reference target not found: samesite
       6

Plus refer to MSIE 3.0x in the past tense (EOL since something like 2003! Should we even remove that bit?), make cookie lowercase, adjust some formatting.

• Issue: Fix all Sphinx reference warnings in the documentation #101100

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📚 Documentation preview 📚: https://cpython-previews--112908.org.readthedocs.build/en/112908/library/http.cookies.html

[AlexWaygood]

Looks great overall! A few small suggestions:

[AlexWaygood]

🍪🎉

[miss-islington-app]

Thanks @hugovk for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11, 3.12.
🐍🍒⛏🤖

[bedevere-app]

GH-112929 is a backport of this pull request to the 3.12 branch.

[bedevere-app]

GH-112930 is a backport of this pull request to the 3.11 branch.