Revert "Fix model switchTo e2e assertion to match runtime behavior"

This reverts commit 001f6f4.

Author: SteveSandersonMS

nodejs/test/e2e/rpc_session_state.e2e.test.ts

@@ -65,7 +65,7 @@ describe("Session-scoped RPC", async () => {
         const after = await session.rpc.model.getCurrent();
 
         expect(result.modelId).toBe("gpt-4.1");
-        expect(after.modelId).toBe("gpt-4.1");
+        expect(after.modelId).toBe(before.modelId);
 
         await session.disconnect();
     });