fix: don't suggest onion peers for channel opening

`suggest_node_channel_open()` did suggest peers with onion hostname,
even if the caller has no proxy enabled. This causes channel openings in
the gui to sometimes just not work and show a `CancelledError()` becaues
it wasn't able to connect to the peer.
Now only clearnet peers will get recommended, as these will always work.

electrum/lnrater.py

@@ -258,6 +258,12 @@ class LNRater(Logger):
             # don't want to connect to nodes we already have a channel with on another device
             if self.lnworker.has_conflicting_backup_with(pk):
                 continue
+            # node should be on clearnet and have an address saved
+            for (hostname, _, _) in self.lnworker.channel_db.get_node_addresses(node_id=pk):
+                if not hostname.endswith(".onion"):
+                    break
+            else:
+                continue
             break
 
         alias = node_info.alias if node_info else 'unknown node alias'