Remove unnecessary ETCD_UNSUPPORTED_ARCH for arm64

we should only use this env var for `arm`, since `arm64` is fully
supported by etcd folks, let us drop this!

(ex - https://github.com/etcd-io/etcd/releases/tag/v3.5.6)

ppc64le comment should be dropped as well

Signed-off-by: Davanum Srinivas <davanum@gmail.com>

hack/lib/etcd.sh

@@ -51,9 +51,7 @@ kube::etcd::validate() {
 
   # need set the env of "ETCD_UNSUPPORTED_ARCH" on unstable arch.
   arch=$(uname -m)
-  if [[ $arch =~ aarch* ]]; then
-	  export ETCD_UNSUPPORTED_ARCH=arm64
-  elif [[ $arch =~ arm* ]]; then
+  if [[ $arch =~ arm* ]]; then
 	  export ETCD_UNSUPPORTED_ARCH=arm
   fi
   # validate installed version is at least equal to minimum