XXX: disable Jenkins node enabling on jenkins-slave.service startup

This yields a 403 with #16955 on my local Jenkins setup.

templates/jenkins/jenkins-slave.service.erb

@@ -4,9 +4,10 @@ Description=Jenkins slave node
 [Service]
 Type=simple
 ExecStartPre=/usr/local/share/jenkins-slave-download <%= @master_url %>
-ExecStartPre=/usr/local/share/jenkins-enable-node \
-    --orchestrator-url <%= @master_url %> \
-    --node-name <%= @domain == "lizard" ? @hostname : @fqdn %>
+# XXX: yields 403 once #16955
+# ExecStartPre=/usr/local/share/jenkins-enable-node \
+#     --orchestrator-url <%= @master_url %> \
+#     --node-name <%= @domain == "lizard" ? @hostname : @fqdn %>
 ExecStart=/usr/bin/java -jar /run/jenkins/slave.jar -jnlpUrl <%= @master_url %>/computer/<%= @node_name %>/slave-agent.jnlp
 User=jenkins
 LimitNOFILE=8192