PEP 101: Updates

[hugovk]

Various updates:

• python-dev@python.org has been archived:
  https://www.mail-archive.com/python-dev@python.org/msg116752.html

• The new branch is created when the last one enters beta

• Move 'add label' instructions to same place

• devguide: 'Feature requests do not need version labels; it is implicit that features are added to the main branch only'
  https://devguide.python.org/triage/labels/#type-labels

• Move instruction on bumping issue versions to branch retirement section

• Link to release PEPs

• We no longer need to update years in copyright notices:
  https://devguide.python.org/getting-started/pull-request-lifecycle/#copyrights

• http -> https, update links, wording

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[ned-deily]

The proposed changes LGTM. But since this is an all-purpose cleanup PR, I suggest also considering:

1. at least add a note about the absence of GPG files starting with 3.14
2. add a step in the End-of-life section about running a final update of the on-line docs with the end-of-life banner (I didn't see any mention of that)

[hugovk]

I was sure number two was there but I can't find it either.

Updated to add both.