add needed ruby:backports repo for SLES

packaging in systemsmanagement:puppet seems to have changed the ruby used while building, resulting in an error:
```
nothing provides /usr/bin/ruby.ruby1.8 needed by rubygem-hiera-1.2.1-13.3.x86_64
```
devel:languages:ruby:backports contains a Ruby 1.8 that fits that need, so pull in that to get Puppet working again.