docs: add proper code block formatting to the docs (#371)

Author: bharatr21

googlemaps/places.py

@@ -477,13 +477,13 @@ def places_photo(client, photo_reference, max_width=None, max_height=None):
     :rtype: iterator containing the raw image data, which typically can be
         used to save an image file locally. For example:
 
-        ```
+    .. code-block:: python
+
         f = open(local_filename, 'wb')
         for chunk in client.places_photo(photo_reference, max_width=100):
             if chunk:
                 f.write(chunk)
         f.close()
-        ```
     """
 
     if not (max_width or max_height):