[Documentation] Fix debug doc (#1903)

Author: jwierzbo

docs/how-to/debugging.md

@@ -32,5 +32,5 @@ helm upgrade --install kube-arangodb \
 
 Then run:
 ```shell
-kubectl exec {POD_kube-arangodb-operator} -- /usr/bin/arangodb_operator debug-package --namespace {namespace} -o - > db.tar.gz
+kubectl exec {POD_kube-arangodb-operator}  --namespace {namespace} -- /usr/bin/arangodb_operator debug-package --namespace {namespace} -o - > db.tar.gz
 ```