fix unit test to use no grad (#3283)

Author: liangel-02

test/quantization/quantize_/workflows/float8/test_float8_tensor.py

@@ -80,6 +80,7 @@ def forward(self, x):
 class TestFloat8Tensor(TorchAOIntegrationTestCase):
     def setUp(self):
         self.GPU_DEVICES = ["cuda"] if torch.cuda.is_available() else []
+        torch.set_grad_enabled(False)
 
     @unittest.skipIf(not torch.cuda.is_available(), "Need CUDA available")
     @unittest.skipIf(