Update Kuberay version in CI. (#27967) (#29151)

Updates KubeRay version used in CI to v0.3.0-rc.2 (which we expect to be identical to the final v0.3.0).
Also removes a couple of old files.

Will open a corresponding cherry pick in the Ray 2.0.0 branch.
The key thing to verify is that the CI autoscaling test passes here and in the PR and in the PR against the 2.0.0 branch.

python/ray/autoscaler/kuberay/init-config.sh

@@ -2,11 +2,10 @@
 
 # Clone pinned Kuberay commit to temporary directory, copy the CRD definitions
 # into the autoscaler folder.
+KUBERAY_COMMIT="v0.3.0-rc.2"
+OPERATOR_TAG="v0.3.0-rc.2"
 
-KUBERAY_SHA="ce84f0441c991eb4b0f52ee2cd85c0a5ac048d11"
-OPERATOR_TAG=${KUBERAY_SHA:0:7}
-
-# Requires Kustomize (dependency to be removed after KubeRay 0.3.0 cut)
+# Requires Kustomize
 if ! command -v kustomize &> /dev/null
 then
     echo "Please install kustomize. Then re-run this script."
@@ -18,12 +17,9 @@ SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
 DIR=$(mktemp -d -t "kuberay-XXXXXX")
 
 pushd "$DIR" || exit
-    git clone https://github.com/ray-project/kuberay/
-    pushd "kuberay" || exit
-        git checkout "$KUBERAY_SHA$"
-        pushd ray-operator/config/default || exit
-            kustomize edit set image kuberay/operator=kuberay/operator:"$OPERATOR_TAG"
-        popd || exit
-        cp -r ray-operator/config "$SCRIPT_DIR/"
+    git clone https://github.com/ray-project/kuberay/ --branch "$KUBERAY_COMMIT" --depth 1
+    pushd kuberay/ray-operator/config/default || exit
+        kustomize edit set image kuberay/operator=kuberay/operator:"$OPERATOR_TAG"
     popd || exit
+    cp -r kuberay/ray-operator/config "$SCRIPT_DIR/"
 popd || exit