Use swish as default activation.

PiperOrigin-RevId: 307057884

official/vision/image_classification/configs/examples/efficientnet/imagenet/efficientnet-b0-gpu.yaml

@@ -34,6 +34,7 @@ model:
       num_classes: 1000
       batch_norm: 'default'
       dtype: 'float32'
+      activation: 'swish'
   optimizer:
     name: 'rmsprop'
     momentum: 0.9

official/vision/image_classification/configs/examples/efficientnet/imagenet/efficientnet-b0-tpu.yaml

@@ -33,6 +33,7 @@ model:
       num_classes: 1000
       batch_norm: 'tpu'
       dtype: 'bfloat16'
+      activation: 'swish'
   optimizer:
     name: 'rmsprop'
     momentum: 0.9

official/vision/image_classification/configs/examples/efficientnet/imagenet/efficientnet-b1-gpu.yaml

@@ -27,6 +27,7 @@ model:
       num_classes: 1000
       batch_norm: 'default'
       dtype: 'float32'
+      activation: 'swish'
   optimizer:
     name: 'rmsprop'
     momentum: 0.9

official/vision/image_classification/configs/examples/efficientnet/imagenet/efficientnet-b1-tpu.yaml

@@ -32,6 +32,7 @@ model:
       num_classes: 1000
       batch_norm: 'tpu'
       dtype: 'bfloat16'
+      activation: 'swish'
   optimizer:
     name: 'rmsprop'
     momentum: 0.9