What does this implement/fix? Explain your changes.

As mentioned in #1180, non-delegate types should not be appear as callable. Removed the ClassObject.tp_call method which seemed to be unused. Also added a test case.

Does this close any currently open issues?

Closes #1180.

Checklist

Check all those that are applicable and complete.

• Make sure to include one or more tests for your change
• If an enhancement PR, please create docs and at best an example
• Add yourself to AUTHORS
• Updated the CHANGELOG