(maint) Remove 'puppet-module-dev' gem dependency

In preparation for the Puppet 7 release, the
puppet-module-posix-dev-r2.7 and puppet-module-posix-dev-r2.7 gems
had to be removed from Gemfile due to the following dependency error:

`puppet-module-posix-dev-r2.7` depends on
  `puppet_litmus` which depends on
    `bolt` which depends on
      `puppet` which is locked to a version below 7

Also added the needed gems that were lost in the above removal process.