Stop using deprecated Element Call URL parameters

These deprecated parameters will be removed very soon (planned for Element Call version 0.15.0) and we no longer have to care about backward compatibility with old versions of Element Call (due to the embedding/bundling work), so now is the right time to migrate.

src/models/Call.ts

@@ -669,12 +669,12 @@ export class ElementCall extends Call {
 
         // Splice together the Element Call URL for this call
         const params = new URLSearchParams({
-            embed: "true", // We're embedding EC within another application
+            confineToRoom: "true", // Only show the call interface for the configured room
             // Template variables are used, so that this can be configured using the widget data.
             skipLobby: "$skipLobby", // Skip the lobby in case we show a lobby component of our own.
             returnToLobby: "$returnToLobby", // Returns to the lobby (instead of blank screen) when the call ends. (For video rooms)
             perParticipantE2EE: "$perParticipantE2EE",
-            hideHeader: "true", // Hide the header since our room header is enough
+            header: "none", // Hide the header since our room header is enough
             userId: client.getUserId()!,
             deviceId: client.getDeviceId()!,
             roomId: roomId,