fix import

Author: vchudnov-g

gapic/templates/%namespace/%name_%version/%sub/__init__.py.j2

@@ -8,7 +8,7 @@ from {{package_path}} import gapic_version as package_version
 __version__ = package_version.__version__
 
 
-import google.api_core
+import google.api_core as api_core
 
 {# How do we get the name of the PyPI path into this template? We
    want the string arguments below to be something like