Update to pyln-client

This updates all plugins *which already have requirements.txt* to
pyln-client from pylightning.

summary/summary.py

@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-from lightning import Plugin, Millisatoshi
+from pyln.client import Plugin, Millisatoshi
 from packaging import version
 from collections import namedtuple
 import lightning