Fix up wrong observers removals

At two occasions (c962f24a and 2b7da566) we have made a mistake while removing observers:

    uninit() {
      // unregister our observer topics
      Services.obs.removeObserver(TorSettingsTopics.SettingChanged, this);
      Services.obs.removeObserver(TorConnectTopics.StateChange, this);
    },

changed milestone to %Tor Browser: 11.0 Issues with previous release

added Doing label

assigned to @richard

mentioned in merge request !238 (merged)

closed with commit b0d3be75

mentioned in commit e1d61123

Cherry-picked onto tor-browser-91.4.1esr-11.0-1 (e1d61123).