(RE-3302) Ensure rpm-builder modules have 3.7 enabled instead 3.4
(RE-3302) Ensure rpm-builder modules have 3.7 enabled instead 3.4

As part of the effort to rename PE 3.4 to PE 3.7, this updates
'3.4' to '3.7' in the existing automation that manages rpm builders.

puppetlabs/puppetlabs-rpmbuilder,puppetlabs/puppetlabs-rpmbuilder