Re-enable matrixchat test (#30410)

Now that we have better logging for our tests
(#30405), I'd like to re-enable
this test so we can try and understsnd what makes it fail.

Author: richvdh

test/unit-tests/components/structures/MatrixChat-test.tsx

@@ -1613,7 +1613,7 @@ describe("<MatrixChat />", () => {
         });
 
         // Flaky test, see https://github.com/element-hq/element-web/issues/30337
-        it.skip("waits for other tab to stop during startup", async () => {
+        it("waits for other tab to stop during startup", async () => {
             fetchMock.get("/welcome.html", { body: "<h1>Hello</h1>" });
             jest.spyOn(Lifecycle, "attemptDelegatedAuthLogin");