Remove "extra" cli option

puppet face applications accept an extra argument, which is forwarded as an options hash to the indirector request, but the argument is unusable. The "--extra" CLI option was added in ae360034c07f9b16467f5ae245ac6d037789ee13 but never worked because you couldn't pass a Hash on the command line. In PUP-8700 the argument was hidden. And in Pupppet 8, we should remove it:

• remove the "--extra" command line argument from: https://github.com/puppetlabs/puppet/blob/180c62d28e7ff1d5c4a72b36308cb4a3f264a487/lib/puppet/indirector/face.rb#L57-L65
• In cases where we were passing options[:extra], such as https://github.com/puppetlabs/puppet/blob/180c62d28e7ff1d5c4a72b36308cb4a3f264a487/lib/puppet/indirector/face.rb#L84, instead pass an empty "{}" which is equivalent to what we were doing before.
• We can probably remove this hack, since "extra" should never be passed through: https://github.com/puppetlabs/puppet/commit/aa3520d059a7a594df78a329339487f881626963

Acceptance Criteria:

When running puppet facts -help there should not be an "-extra" option in documentation.