[#4701] Add missing data migration for the global config and zip mimetypes

[vaszig]

Closes #4701

Changes

• Added missing migration for the global configuration. When we define a global setting for the allowed file types we need to make sure the extra .zip mimetypes are in the list as well.

Checklist

Check off the items that are completed or not relevant.

• Impact on features

  • [x] Checked copying a form
  • [x] Checked import/export of a form
  • [x] Config checks in the configuration overview admin page
  • [x] Problem detection in the admin email digest is handled

• Release management

  • [x] I have labelled the PR as "needs-backport" accordingly

• I have updated the translations assets (you do NOT need to provide translations)

  • [x] Ran ./bin/makemessages_js.sh
  • [x] Ran ./bin/compilemessages_js.sh

• Commit hygiene

  • [x] Commit messages refer to the relevant Github issue
  • [x] Commit messages explain the "why" of change, not the how

[sergei-maertens]

Cherrypicked the commit to stable/2.7.x, stable/2.8.x and master.