chore: do not log UnknownSpeakerError

src/thsf/__init__.py

@@ -63,7 +63,7 @@ def get_speaker_biography(name):
     logging.info(speaker_info)
     return speaker_info["results"][0]["biography"].strip()
   except Exception as err:
-    logging.error(f"UnknownSpeakerError: {name}")
+    logging.debug(f"UnknownSpeakerError: {name}")
     return None
 
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