Update camera_pi.py

Making python editors happy by removing the unused var `foo`

Author: gipsy86147

camera_pi.py

@@ -12,7 +12,7 @@ def frames():
             time.sleep(2)
 
             stream = io.BytesIO()
-            for foo in camera.capture_continuous(stream, 'jpeg',
+            for _ in camera.capture_continuous(stream, 'jpeg',
                                                  use_video_port=True):
                 # return current frame
                 stream.seek(0)