doc: quick start / installation / OpenSUSE: improve link

I believe on the old link it isn't easy to find what to do to "install"
the package.  The new one seems much more user-friendly.

- cherry picked from
  commit 008fbed9 (upstream/operators-guide)
  Author: Vladimír Čunát <vladimir.cunat@nic.cz>
  Date:   2020-01-07 11:23:02 +0100