Remove unused websockets dependency

chattolib provides its own WebSocket implementation, so the explicit
websockets dependency is no longer needed.

pyproject.toml

@@ -13,7 +13,6 @@ authors = [
 ]
 dependencies = [
     "chattolib[realtime]>=0.4.19",
-    "websockets>=13.0",
 ]
 
 [project.optional-dependencies]