Replace openSUSE experimental check with newer version
We're migrating now to openSUSE 15.0 (yes, 15.0 is newer than 42.3),
remove legacy job and replace with native Zuul v3 job running python3.
Depends-On:
- ^setup.cfg$
- ^tools/.*$
- ^tox.ini$
- - legacy-tempest-dsvm-neutron-full-opensuse-423:
+ - tempest-full-py3-opensuse150:
irrelevant-files:
- ^(test-|)requirements.txt$
- ^.*\.rst$
