Disable audiosettings button on Firefox as it is not supported

react/features/toolbox/components/web/AudioSettingsButton.js

      */
     render() {
         const { isDisabled, onAudioOptionsClick, visible } = this.props;
-        const settingsDisabled = !this.state.hasPermissions || isDisabled;
+        const settingsDisabled = !this.state.hasPermissions
+            || isDisabled
+            || !JitsiMeetJS.mediaDevices.isMultipleAudioInputSupported();
 
         return visible ? (
             <AudioSettingsPopup>