Update kubectl_completion.md

Quote shell commands to improve format

docs/user-guide/kubectl/kubectl_completion.md

@@ -11,17 +11,19 @@ Output shell completion code for the given shell (bash or zsh).
 
 This command prints shell code which must be evaluation to provide interactive completion of kubectl commands.
 
-  $ source <(kubectl completion bash)
+  `$ source <(kubectl completion bash)`
 
 will load the kubectl completion code for bash. Note that this depends on the bash-completion framework. It must be sourced before sourcing the kubectl completion, e.g. on the Mac:
 
+```
   $ brew install bash-completion
   $ source $(brew --prefix)/etc/bash_completion
   $ source <(kubectl completion bash)
+```
 
 If you use zsh [1], the following will load kubectl zsh completion:
 
-  $ source <(kubectl completion zsh)
+  `$ source <(kubectl completion zsh)`
 
  [1] zsh completions are only supported in versions of zsh >= 5.2