Remove [Mail Editor] module from [Varbase Core] on the 9.0.x Drupal 9 branch

Problem/Motivation

Requires Drupal: 8.x
composer require did not work
No stable release yet. only 8.x-1.x-dev
Mail Editor is not supporting Drupal 9
And
#3069218: Offering to co-maintain Mail Editor

Proposed resolution

• Remove the Mail Editor module.
• If they made it to Drupal 9, it can be put back.
• Could be forked and add the functional edit in Varbase Mail with better LTR - RTL support