chore: Fix file name reference in Dockerfile (#287)

Author: HKWinterhalter

examples/cloud_run_cloud_events/Dockerfile

@@ -12,7 +12,7 @@ COPY . .
 # Install production dependencies.
 RUN pip install gunicorn cloudevents functions-framework
 RUN pip install -r requirements.txt
-RUN chmod +x send_cloudevent.py
+RUN chmod +x send_cloud_event.py
 
 # Run the web service on container startup.
 CMD ["functions-framework", "--target=hello", "--signature-type=cloudevent"]