gelu -> quick_gelu in hlb_cifar (#3147)

89 -> 86 seconds, same eval acc

examples/hlb_cifar10.py

@@ -49,13 +49,13 @@ class ConvGroup:
     x = x.float()
     x = self.norm1(x)
     x = x.cast(dtypes.default_float)
-    x = x.gelu()
+    x = x.quick_gelu()
     residual = x
     x = self.conv2(x)
     x = x.float()
     x = self.norm2(x)
     x = x.cast(dtypes.default_float)
-    x = x.gelu()
+    x = x.quick_gelu()
 
     return x + residual
 
@@ -64,7 +64,7 @@ class SpeedyResNet:
     self.whitening = W
     self.net = [
       nn.Conv2d(12, 32, kernel_size=1, bias=False),
-      lambda x: x.gelu(),
+      lambda x: x.quick_gelu(),
       ConvGroup(32, 64),
       ConvGroup(64, 256),
       ConvGroup(256, 512),