docs: Update maintainer release checklist with v0.6.3 notes

[matthewfeickert]

Description

Resolves #1578

Update the release checklist for project maintainers with notes taken during the pyhf v0.6.3 release process

Checklist Before Requesting Reviewer

• Tests are passing
• "WIP" removed from the title of the pull request
• Selected an Assignee for the PR to be responsible for the log summary

Before Merging

For the PR Assignees:

• Summarize commit messages into a comprehensive review of the PR

* Update the release checklist for project maintainers with notes taken during the pyhf v0.6.3 release process
   - Add check for copying release notes into GitHub release
   - Add check for Zenodo metadata consistency
   - Add check for Conda-forge feedstock requirements matching those of the GitHub project

[codecov]

Codecov Report

Merging #1597 (78fda8a) into master (4b5389d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1597   +/-   ##
=======================================
  Coverage   97.70%   97.70%           
=======================================
  Files          63       63           
  Lines        4050     4050           
  Branches      576      576           
=======================================
  Hits         3957     3957           
  Misses         54       54           
  Partials       39       39           

Flag	Coverage Δ
contrib	25.43% <ø> (ø)
unittests	97.48% <ø> (ø)

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