Urgency hint enabled by default depending on sound

Make the urgency hint tweak for push rules actions enabled by default if
the rule also has the sound tweak enabled, instead of highlight tweak.

src/backend/nio_callbacks.py

@@ -822,7 +822,7 @@ class NioCallbacks:
                 high   = tweaks.get("highlight", False) is not False
                 bubble = tweaks.get("bubble", notify) is not False
                 sound  = str(tweaks.get("sound") or "")
-                hint   = tweaks.get("urgency_hint", high) is not False
+                hint   = tweaks.get("urgency_hint", bool(sound)) is not False
 
                 model[kind.value, rule.id] = PushRule(
                     id           = (kind.value, rule.id),