Update functional.scaled_dot_product_attention signature/arguments

[DillionLowry]

• Add optional scale and enable_gqa arguments to torch.nn.functional.scaled_dot_product_attention. Default values scale = null and enable_gqa = false match pytorch.

Breaking Change:

• torch.nn.functional.scaled_dot_product_attention's function signature has been changed. The is_casual argument has been renamed to is_causal to match pytorch.

[DillionLowry]

@dotnet-policy-service agree