fix(cleanup): Decouple/Remove openy_myy

[podarok]

Requested-by: @podarok
Decoupled-to: https://github.com/open-y-subprojects/openy_myy

Original Issue, this PR is going to fix: https://openy.atlassian.net/browse/MAINTAIN-118

Make sure these boxes are checked before asking for review of your pull request - thank you!

If there is a new feature or this is a bug fix - use 9.x-2.x branch. We'll tag for release if the bug is critical asap or tag for release next bug fix release until critical issue arrived.

Steps for review

• Ensure code is removed.
• Ensure no dependencies elsewhere in Open Y https://github.com/ymcatwincities/openy/search?l=YAML&q=openy_myy
• Check https://github.com/open-y-subprojects/openy_myy/releases/tag/1.0
• Check https://packagist.org/packages/open-y-subprojects/openy_myy

General checks

• All coding styles are fulfilled and there are no any issues reported by CodeSniffer. See Code of Conduct.
• Try to use Conventional commit messages accordingly to the standard https://www.conventionalcommits.org/en/v1.0.0/#specification
• Documentation has been updated according to PR changes.
• Steps for review have been provided according to PR changes.
  
• Make sure you've provided all necessary hook_update_N to support upgrade path.
• Make sure your git email is associated with account on drupal.org, otherwise you won't get commits there.
  
• If you would like to get credits on drupal.org, check documentation.

Thank you for your contribution!

[gundevel]

Build comment file:

Check Open Y Installation Wizard at http://install.openy.cibox.tools/build3294/install.php

---

Test PASSed.
Refer to this link for build results (access rights to CI server needed):
http://openy.cibox.tools:8080/job/PR_BUILDER_COMPOSER/3294/

[gundevel]

Open Y Upgrade Path site check installed at http://upgrade.openy.cibox.tools/build3294/