Fix syntax in az extension remove command

for containerapps cli extension

Author: apwestgarth

articles/container-apps/azure-arc-enable-cluster.md

@@ -57,7 +57,7 @@ az extension add --source https://aka.ms/acaarccli/containerapp-latest-py2.py3-n
 az extension add --name connectedk8s  --upgrade --yes
 az extension add --name k8s-extension --upgrade --yes
 az extension add --name customlocation --upgrade --yes
-az extension az extension remove --name containerapp
+az extension remove --name containerapp
 az extension add --source https://aka.ms/acaarccli/containerapp-latest-py2.py3-none-any.whl --yes
 ```