Revert "A quick hack until fixing the freezing properly"

This reverts commit 33befb8.

Author: Neil Booth

electrumx/server/session.py

@@ -567,11 +567,9 @@ async def _notify_sessions(self, height, touched):
             for hashX in set(hc).intersection(touched):
                 del hc[hashX]
 
-        # FIXME
-        async with ignore_after(15):
-            async with TaskGroup() as group:
-                for session in self.sessions:
-                    await group.spawn(session.notify(touched, height_changed))
+        async with TaskGroup() as group:
+            for session in self.sessions:
+                await group.spawn(session.notify(touched, height_changed))
 
     def add_session(self, session):
         self.sessions.add(session)