(maint) avoid using Command API for new provider example

[DavidS]

The Command API is scheduled to be removed. This is a simpler example
which also better explains what needs to happen in a provider.

[DavidS]

david@davids:~/git/tmp/test$ pdk new provider test
pdk (INFO): Creating '/home/david/git/tmp/test/lib/puppet/type/test.rb' from template.
pdk (INFO): Creating '/home/david/git/tmp/test/lib/puppet/provider/test/test.rb' from template.
pdk (INFO): Creating '/home/david/git/tmp/test/spec/unit/puppet/provider/test/test_spec.rb' from template.
david@davids:~/git/tmp/test$ pdk validate --parallel
pdk (INFO): Running all available validators...
┌ [✔] Validating module using 3 threads
├──[✔] Checking Ruby code style (**/**.rb).
├──[✔] Checking metadata syntax (metadata.json tasks/*.json).
└──[✔] Checking module metadata style (metadata.json).
info: puppet-syntax: ./: Target does not contain any files to validate (**/**.pp).
info: puppet-lint: ./: Target does not contain any files to validate (**/*.pp).
info: task-metadata-lint: ./: Target does not contain any files to validate (tasks/*.json).
david@davids:~/git/tmp/test$ pdk test unit
[✔] Preparing to run the unit tests.
[✔] Running unit tests.
  Evaluated 4 tests in 0.012141885 seconds: 0 failures, 0 pending.
[✔] Cleaning up after running unit tests.
david@davids:~/git/tmp/test$ 

for reference.