Plasma 5.8 schedule update

[Jonathan Riddell]

As discussed on this list and in meetings I've updated the 5.8 release
schedule at SuSE's request making the repo freeze during akademy and
the release two weeks earlier at the end of september/start of
october.  Other dates become two weeks earlier too.

https://community.kde.org/Schedules/Plasma_5

https://calendar.google.com/calendar/embed?src=031gkgqg1hjf8lcmj0em1d2sj8%40group.calendar.google.com&ctz=Europe/London

that puts 5.8.5 between christmas and new year which might not be a great idea

We're pleased to help support long term committed patrons such as SuSE.

Jonathan