wee-slack: fix wrong dependency

[caioalonso]

The current python-websockets-client dependency is incorrect:

│14:56:15     | python: stdout/stderr (?): Traceback (most recent call last):
│14:56:15     | python: stdout/stderr (?):   File "/home/caio/.weechat/python/autoload/wee_slack.py", line 28, in <module>
│14:56:15     | python: stdout/stderr (?):     from websocket import ABNF, create_connection, WebSocketConnectionClosedException
│14:56:15     | python: stdout/stderr (?): ModuleNotFoundError: No module named 'websocket'
│14:56:15 =!= | python: unable to parse file "/home/caio/.weechat/python/autoload/wee_slack.py"

Changing it to python3-websockets-client fixes the issue.

[Hoshpak]

now please squash the two commits into one.

[caioalonso]

@Hoshpak done.