[ticket/11670] Consistency with logo: Replace "phpBB(tm)" with "phpBB(R)".

PHPBB3-11670
Merge remote-tracking branch 'github-bantu/ticket/11670' into prep-release-3.0.12

* github-bantu/ticket/11670:
  [ticket/11670] Consistency with logo: Replace "phpBB(tm)" with "phpBB(R)".