removed api_core from mypy install

Author: daniel-sanche

noxfile.py

@@ -133,7 +133,6 @@ def format(session):
 def mypy(session):
     """Verify type hints are mypy compatible."""
     session.install("-e", ".")
-    session.install("-e", "python-api-core")
     session.install(
         "mypy",
         "types-setuptools",