Ensure our Semaphore is kept in line with the buffer length

Author: blast-hardcheese

src/replit_river/common_session.py

@@ -166,15 +166,18 @@ async def buffered_message_sender(
                     type(e),
                     exc_info=e,
                 )
+                message_enqueued.release()
                 break
             except FailedSendingMessageException:
                 logger.error(
                     "Failed sending message, waiting for retry from buffer",
                     exc_info=True,
                 )
+                message_enqueued.release()
                 break
             except Exception:
                 logger.exception("Error attempting to send buffered messages")
+                message_enqueued.release()
                 break