fix: Mark test types as not a module

When attempting to run tests from the IDE I was running into dependencies which were importing types from the test module.

It seems to be a well-known problem:

 - https://stackoverflow.com/questions/36669895/site-py-attributeerror-module-object-has-no-attribute-moduletype-upon-runn
 - https://stackoverflow.com/questions/36250353/importing-a-library-from-or-near-a-script-with-the-same-name-raises-attribute

And the quick solution is just to remove the __init__ from the test types module.

Author: zastrowm