[ticket/11752] HTTP -> HTTPs in email/installed.txt

PHPBB3-11752
Merge remote-tracking branch 'bantu/ticket/11752' into prep-release-3.0.12

* bantu/ticket/11752:
  [ticket/11752] HTTP -> HTTPs in email/installed.txt
Merge branch 'prep-release-3.0.12' into develop-olympus

* prep-release-3.0.12:
  [ticket/11752] HTTP -> HTTPs in email/installed.txt