feat: Remove the startBitrate and minBitrate conference-request options. (#2194)

modules/xmpp/moderator.js

     const config = this.options;
     const properties = {};
 
-    if (config.startBitrate) {
-        properties.startBitrate = config.startBitrate;
-    }
-    if (config.minBitrate) {
-        properties.minBitrate = config.minBitrate;
-    }
-
     if (config.startAudioMuted !== undefined) {
         properties.startAudioMuted = config.startAudioMuted;
     }