Parts of the release process are outdated or don't make sense.
Changes include:
* Revision of "Check configuration" section, as it does not check anything configuration related.
* Moved the "Verify tests passed" section to after the "Update documents / code..." since tests
should always be run on the release candidate.
* Moved items in the wrong sections to places that make more sense.
* Removed references to disk size expectations, as these were duplicated, outdated, and are now handled by automation.
* Reworded notes on updating chainparams and seeds.
* Simplified pushing to Github since the commits are automated.
* Removed the note about updating the version number on bitcoinabc.org since `/latest` effectively
does this for us.