[autoscaler][aws] Fix example minimal (ray-project#27075)

Why are these changes needed?
The DLAMI moved underneath us and broke for 2 reasons.

The AMI's snapshot size increased to 140 GB which was more than our hardcoded max EBS volume size of 100GB
The AMI dropped support for python 3.7 and only has 3.8 now.
The solutions short term solutions are simple.

Allocate a bigger EBS volume.
Use the tensorflow 3.8 env.
Related issue number
Closes ray-project#26368

Co-authored-by: Alex <alex@anyscale.com>
Signed-off-by: Frank Luan <lsf@berkeley.edu>

python/ray/autoscaler/aws/defaults.yaml

@@ -60,7 +60,7 @@ available_node_types:
  BlockDeviceMappings:
  - DeviceName: /dev/sda1
  Ebs:
- VolumeSize: 100
+ VolumeSize: 256
  # Additional options in the boto docs.
  ray.worker.default:
  # The minimum number of nodes of this type to launch.
@@ -122,9 +122,9 @@ initialization_commands: []
 # List of shell commands to run to set up nodes.
 setup_commands:
  - >-
- (stat $HOME/anaconda3/envs/tensorflow2_latest_p37/ &> /dev/null &&
- echo 'export PATH="$HOME/anaconda3/envs/tensorflow2_latest_p37/bin:$PATH"' >> ~/.bashrc) || true
- - which ray || pip install -U "ray[default] @ https://s3-us-west-2.amazonaws.com/ray-wheels/latest/ray-3.0.0.dev0-cp37-cp37m-manylinux2014_x86_64.whl"
+ (stat $HOME/anaconda3/envs/tensorflow2_p38/ &> /dev/null &&
+ echo 'export PATH="$HOME/anaconda3/envs/tensorflow2_p38/bin:$PATH"' >> ~/.bashrc) || true
+ - which ray || pip install -U "ray[default] @ https://s3-us-west-2.amazonaws.com/ray-wheels/latest/ray-3.0.0.dev0-cp38-cp38-manylinux2014_x86_64.whl"
 
 # Custom commands that will be run on the head node after common setup.
 head_setup_commands: