Fix comment: pulsar.Client.create_producer() (#7972)

Correct argument name is `send_timeout_millis` not `send_timeout_seconds`

pulsar-client-cpp/python/pulsar/__init__.py

@@ -473,7 +473,7 @@ class Client:
            published by the producer. First message will be using
            `(initialSequenceId + 1)`` as its sequence id and subsequent messages will
            be assigned incremental sequence ids, if not otherwise specified.
-        * `send_timeout_seconds`:
+        * `send_timeout_millis`:
           If a message is not acknowledged by the server before the
           `send_timeout` expires, an error will be reported.
         * `compression_type`: