[Docs] Fix call to deprecated function (pytorch#135037)

Pull Request resolved: pytorch#135037
Approved by: https://github.com/janeyx99, https://github.com/jbschlosser

torch/nn/functional.py

@@ -5844,7 +5844,7 @@ def forward(self, ...):
         >>> query = torch.rand(32, 8, 128, 64, dtype=torch.float16, device="cuda")
         >>> key = torch.rand(32, 8, 128, 64, dtype=torch.float16, device="cuda")
         >>> value = torch.rand(32, 8, 128, 64, dtype=torch.float16, device="cuda")
-        >>> with torch.backends.cuda.sdp_kernel(enable_math=False):
+        >>> with sdpa_kernel(backends=[SDPBackend.FLASH_ATTENTION]):
         >>>     F.scaled_dot_product_attention(query,key,value)