removed extra hyphen in kubectl book

Author: oke-py

staging/src/k8s.io/kubectl/docs/book/pages/resource_printing/queries_and_options.md

@@ -113,7 +113,7 @@ kubectl get deployments -l app=nginx
 By default Get and Describe will fetch resource in the default namespace or the namespace specified
 with `--namespace`.
 
-The `---all-namespaces` flag will **fetch Resources from all namespaces**.
+The `--all-namespaces` flag will **fetch Resources from all namespaces**.
 
 {% sample lang="yaml" %}