Include alpha to fix aten.sub.Tensor (#2418)

Summary:
Pull Request resolved: #2418

Missed this in #2366
ghstack-source-id: 218593311
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Reviewed By: SS-JIA

Differential Revision: D54880024

fbshipit-source-id: c4e19d8fefbb9d2fc4547ec2edc236060638da5e

Author: Jorge Pineda

backends/vulkan/runtime/graph/ops/glsl/all_shaders.yaml

@@ -19,7 +19,7 @@ binary_op:
   shader_variants:
     - NAME: binary_add
     - NAME: binary_sub
-      OPERATOR: X - Y
+      OPERATOR: X - A * Y
     - NAME: binary_mul
       OPERATOR: X * Y
     - NAME: binary_div

backends/vulkan/test/test_vulkan_delegate.py

@@ -124,8 +124,8 @@ def __init__(self):
                 self.weight = torch.rand(size=(2, 3), dtype=torch.float32)
 
             def forward(self, x, y):
-                z = x + y
-                z = z + x
+                z = torch.add(x, y, alpha=2)
+                z = torch.add(x, y, alpha=3.14)
                 z = z + x
                 z = z + self.weight
                 return z
@@ -144,8 +144,8 @@ def __init__(self):
                 super().__init__()
 
             def forward(self, x, y):
-                z = x - y
-                z = z - x
+                z = torch.sub(x, y, alpha=2)
+                z = torch.sub(z, x, alpha=3.14)
                 z = z - x
                 return z