Merge pull request smallstep#367 from smallstep/herman-sudo-agent-register

Author: hslatman

platform/smallstep-agent.mdx

@@ -191,7 +191,7 @@ curl -sL https://packages.smallstep.com/scripts/smallstep-agent-install.sh | sud
 To configure the agent and register your Linux device with your Smallstep team, run:
 
 ```jsx
-step-agent-plugin register [team name]
+sudo step-agent-plugin register [team name]
 ```
 
 Alternatively, you can configure the agent manually.