PEP 565: Fix footnotes

[hugovk]

Fix these warnings:

pep-0565.rst:337: WARNING: Footnote [1] is not referenced.
pep-0565.rst:340: WARNING: Footnote [2] is not referenced.
pep-0565.rst:343: WARNING: Footnote [3] is not referenced.
pep-0565.rst:346: WARNING: Footnote [4] is not referenced.
pep-0565.rst:349: WARNING: Footnote [5] is not referenced.
pep-0565.rst:352: WARNING: Footnote [6] is not referenced.
pep-0565.rst:355: WARNING: Footnote [7] is not referenced.
pep-0565.rst:358: WARNING: Footnote [8] is not referenced.
pep-0565.rst:361: WARNING: Footnote [9] is not referenced.

1-5 and 8-9 were of the format [1_] instead of [1]_.

6-7 are not referred to, so changed those to bullet points.

And then renumbered 8-9 to 6-7.

---

Also:

• Consistently format DeprecationWarning as DeprecationWarning to match the majority in this document
• Replace BPO links with GitHub
• Remove redundant emacs metadata

Preview

https://pep-previews--2741.org.readthedocs.build/pep-0565/

[CAM-Gerlach]

Two small related comments, otherwise LGTM

[CAM-Gerlach]

LGTM, thanks @hugovk !