Tweaked the openSUSE build service links

This adds links to the openSUSE wiki with further information
* https://en.opensuse.org/OpenRA
* https://en.opensuse.org/Games

and avoids linking the download page twice. Also it may be confusing that you don't get a package, but another HTML site with instructions. I tried to mitigate that by renaming the button a bit.
The original idea was to have the same wording for all of these outside sources.  The download section on https://en.opensuse.org/OpenRA also links back to here with the now-obsolete #rpm section.