(CPR-768) Update github workflow to build on pushes to 'main' branch
(CPR-768) Update github workflow to build on pushes to 'main' branch

I think the differences in the workflow between 6.x (the default branch)
and main (the branch we build from) was the source of the issues.

puppetlabs/puppet-server,puppetlabs/puppet-server,puppetlabs/puppetserver,puppetlabs/puppetserver,puppetlabs/puppetserver,puppetlabs/puppetserver,puppetlabs/puppet-server