chore: add doc around getMessageReplaced

Signed-off-by: Samuel Anderson <[email protected]>

src/deadline_worker_agent/log_messages.py

@@ -660,6 +660,8 @@ def filter(self, record: logging.LogRecord) -> bool:
         if isinstance(record.msg, str):
             message = record.getMessage()
             record.msg = StringLogEvent(message)
+            # We must replace record.getMessage() so that a string is returned and not the LogEvent type.
+            # getMessageReplaced is used to indicate we already have done so, to avoid replacing twice.
             record.getMessageReplaced = True
             record.getMessage = MethodType(lambda self: self.msg.getMessage(), record)  # type: ignore
             record.args = None