[ticket/12645] Replace support links in SUPPORT_BODY with 3.1 links

PHPBB3-12645
Merge remote-tracking branch 'nickvergessen/ticket/12645' into develop-ascraeus

* nickvergessen/ticket/12645:
  [ticket/12645] Replace support links in SUPPORT_BODY with 3.1 links
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12645] Replace support links in SUPPORT_BODY with 3.1 links