(CAT-273) Remove plan exclusion from rake tasks

The plan exclusion was originally added to the rake tasks due to Bolt
not being able to handle syntax for them. This was the case 6 years ago
but not anymore. Therefore, we can remove the exclusion from the rake.

Author: LukasAud

lib/puppetlabs_spec_helper/rake_tasks.rb

@@ -191,7 +191,6 @@
 PuppetSyntax.exclude_paths << 'pkg/**/*'
 PuppetSyntax.exclude_paths << 'vendor/**/*'
 PuppetSyntax.exclude_paths << '.vendor/**/*'
-PuppetSyntax.exclude_paths << 'plans/**/*'
 PuppetSyntax.check_hiera_keys = true
 PuppetSyntax.check_hiera_data = true