[ticket/12697] Delete cached extension schema.json files after testing

PHPBB3-12697
Merge pull request #2580 from VSEphpbb/ticket/12697

[ticket/12697] Delete cached extension schema.json files after testing

* VSEphpbb/ticket/12697:
  [ticket/12697] Delete cached extension schema.json files after testing
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12697] Delete cached extension schema.json files after testing