config: switch default disableRtx to false

config.js

     enableUserRolesBasedOnToken: false,
     // Suspending video might cause problems with audio playback. Disabling until these are fixed.
     disableSuspendVideo: true,
-    // disables or enables RTX (RFC 4588).
-    disableRtx: true,
+    // disables or enables RTX (RFC 4588) (defaults to false).
+    disableRtx: false,
     // Sets the preferred resolution (height) for local video. Defaults to 360.
     resolution: 720
 };