wikipedia: log failure details using DEBUG level

Co-authored-by: dgw <[email protected]>

Author: SnoopJ

sopel/modules/wikipedia.py

@@ -309,7 +309,9 @@ def mw_image_description(server, image):
         raw_desc = page["imageinfo"][0]["extmetadata"]["ImageDescription"]["value"]
 
     except LookupError:
-        LOGGER.exception("Error getting image description for %r, response was: %r", image, json)
+        LOGGER.debug(
+            "Error getting image description for %r, response was: %r",
+            image, json, exc_info=True)
         return None
 
     # Some descriptions contain markup, use WikiParser to discard that