Bug 21782: Release team 18.11 in About

Bug 21782: Release team 18.11 in About

[1] Moved the (usual) 18.05 positions to the Dev section.
[2] Added the 18.11 positions to the Release team section.

Test plan:
[1] Look at About/Koha team.
[2] Compare with roles 18.05 and roles 18.11.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>