fix: double call to 'span.end()' when 'acknowledge' is called

The `trace.use_span(span, True)` will already close this span,
if we store this same span in the message, it'll be closed
by a call to any of the `*acknowledge` functions, essentially
causing a double call to `span.end()`.

This change prevents this from happening by not storing the
span in the message.

Author: JonathanxD

Diff for: instrumentation/opentelemetry-instrumentation-pulsar/src/opentelemetry/instrumentation/pulsar/__init__.py

@@ -142,7 +142,6 @@ def wrapper(  # pylint: disable=function-redefined
             message.partition_key(),
         )
         _enrich_span_with_message(span, message)
-        message._set_current_span(span)
         with trace.use_span(span, True):
             return message_listener(consumer, message, *args, **kwargs)