fix: duck on audio packets only, remove unmute-based ducking

Instant ducking is purely packet-based now -- _instant_duck() fires
on _on_sound_received, not on user state changes. Removes the
USERUPDATED callback that preemptively ducked on unmute.

src/derp/mumble.py

@@ -20,7 +20,6 @@ from pymumble_py3.constants import (
     PYMUMBLE_CLBK_DISCONNECTED,
     PYMUMBLE_CLBK_SOUNDRECEIVED,
     PYMUMBLE_CLBK_TEXTMESSAGERECEIVED,
-    PYMUMBLE_CLBK_USERUPDATED,
 )
 
 from derp.bot import _TokenBucket
@@ -218,10 +217,6 @@ class MumbleBot:
             PYMUMBLE_CLBK_SOUNDRECEIVED,
             self._on_sound_received,
         )
-        self._mumble.callbacks.set_callback(
-            PYMUMBLE_CLBK_USERUPDATED,
-            self._on_user_updated,
-        )
         self._mumble.set_receive_sound(self._receive_sound)
         self._mumble.start()
         self._mumble.is_ready()
@@ -326,26 +321,6 @@ class MumbleBot:
             except Exception:
                 log.exception("mumble: sound listener error")
 
-    def _on_user_updated(self, user, actions) -> None:
-        """Callback from pymumble thread: user state changed.
-
-        When a non-bot user unmutes, update ``_voice_ts`` and snap duck
-        volume to floor immediately.
-        """
-        if "self_mute" not in actions:
-            return
-        name = user["name"] if isinstance(user, dict) else None
-        bots = getattr(self.registry, "_bots", {})
-        if name and name in bots:
-            return
-        # Only care about unmute (self_mute going False)
-        if user.get("self_mute", True):
-            return
-        log.info("mumble: %s unmuted, preemptive duck", name or "?")
-        self._last_voice_ts = time.monotonic()
-        self.registry._voice_ts = self._last_voice_ts
-        self._instant_duck()
-
     def _on_text_message(self, message) -> None:
         """Callback from pymumble thread: text message received.