Removes listener to missing event and duplicate dialog code.

conference.js

@@ -813,10 +813,6 @@ export default {
             APP.UI.updateDTMFSupport(isDTMFSupported);
         });
 
-        room.on(ConferenceEvents.FIREFOX_EXTENSION_NEEDED, function (url) {
-            APP.UI.notifyFirefoxExtensionRequired(url);
-        });
-
         APP.UI.addListener(UIEvents.ROOM_LOCK_CLICKED, () => {
             if (room.isModerator()) {
                 let promise = roomLocker.isLocked

modules/UI/UI.js

@@ -736,21 +736,6 @@ UI.notifyConnectionFailed = function (stropheErrorMsg) {
     );
 };
 
-/**
- * Notify user that he need to install Firefox extension to share screen.
- * @param {stirng} url extension url
- */
-UI.notifyFirefoxExtensionRequired = function (url) {
-    messageHandler.openMessageDialog(
-        "dialog.extensionRequired",
-        null,
-        null,
-        APP.translation.generateTranslationHTML(
-            "dialog.firefoxExtensionPrompt", {url}
-        )
-    );
-};
-
 /**
  * Notify user that he was automatically muted when joned the conference.
  */