Add pyln-client requirement to all plugins

persistent-channels/persistent-channels.py

@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-from lightning import Plugin, RpcError
+from pyln.client import Plugin, RpcError
 from threading import Timer
 import os
 import json

persistent-channels/requirements.txt

@@ -1 +1 @@
-pylightning==0.0.6
+pyln-client>=0.7.3