use clear instead of {}

at:

https://github.com/noplay/python-mysql-replication/blob/511b42c8ac2c1682a6e2fd4d6691658245b57987/pymysqlreplication/binlogstream.py#L469

we should use `.clear()` instead of `={}`

https://stackoverflow.com/questions/369898/difference-between-dict-clear-and-assigning-in-python

Open pymysqlreplication/binlogstream.py at line 469 and inspect the assignment in context. Replace the assignment with .clear() as described, then verify the project's existing checks pass and that the dictionary is cleared at that point.

Written by the indexing model from the issue text.