[Fix #10216] Update the release documentation with feedback from the 21.7.0 release.

[adiroiban]

Scope and purpose

This is a minor release doc update while doing an actual release.

Updated docs at https://twisted--1616.org.readthedocs.build/en/1616/core/development/policy/release-process.html

Contributor Checklist:

• The associated ticket in Trac is here: https://twistedmatrix.com/trac/ticket/10216
• [NA] I ran tox -e lint to format my patch to meet the Twisted Coding Standard
• I have created a newsfragment in src/twisted/newsfragments/ (see: News files)
• The title of the PR starts with the associated Trac ticket number (without the # character).
• [NA] I have updated the automated tests and checked that all checks for the PR are green.
• I have submitted the associated Trac ticket for review by adding the word review to the keywords field in Trac, and putting a link to this PR in the comment; it shows up in https://twisted.reviews/ now.
• The merge commit will use the below format
  The first line is automatically generated by GitHub based on PR ID and branch name.
  The other lines generated by GitHub should be replaced.

Merge pull request #123 from twisted/4356-branch-name-with-trac-id

Author: adiroiban
Reviewer: 
Fixes: ticket:10216

Update the release documentation.

[adiroiban]

The main changes is making it clear that a review for a release candidate should be asked only after the RC is published on PyPI,

But maybe we should ask a review before pushing a PR.

Also, before starting the release branch, a message can be sent to IRC or mailing list to see if there is any PR for which the release can be delayed with 1 or 2 days... but not longer.
But maybe we don't need to document this and any release manager can do it or not.

Or just a info that as an optional step, the release manager can communicate the intention of a release .

---

Quick link for the review https://twisted--1616.org.readthedocs.build/en/1616/core/development/policy/release-process.html

[graingert]

broken URL scheme

[adiroiban]

Thanks @graingert for the review. Much appreciated.

I am still updating these notes while working on the release.

I will send one final review request after the final Twisted 21.7.0 is out.

[adiroiban]

This is ready for a final review.
I left my comments based on the latest release experience.

For now, read the docs updates are manual ... I hope it can be fixed in #1629
but the documentation should for now mention that after the release you need to manually create the documentation for the tag.