Update the display of decryption failures due to failed trust requirement (#28300)

* update the display of decryption failures due to failed trust requirement

* add test for not showing shield

playwright/e2e/crypto/invisible-crypto.spec.ts

@@ -51,6 +51,6 @@ test.describe("Invisible cryptography", () => {
         /* should show an error for a message from a previously verified device */
         await bobSecondDevice.sendMessage(testRoomId, "test encrypted from user that was previously verified");
         const lastTile = page.locator(".mx_EventTile_last");
-        await expect(lastTile).toContainText("Verified identity has changed");
+        await expect(lastTile).toContainText("Sender's verified identity has changed");
     });
 });