modify the example part of missingResourceError

"missingResourceError" is a generic error for kubectl, so we should
not use concrete examples in the error message.

pkg/kubectl/resource/builder.go

@@ -84,8 +84,8 @@ var missingResourceError = fmt.Errorf(`You must provide one or more resources by
 Example resource specifications include:
    '-f rsrc.yaml'
    '--filename=rsrc.json'
-   'pods my-pod'
+   '<resource> <name>'
-   'services'`)
+   '<resource>'`)
 
 // TODO: expand this to include other errors.
 func IsUsageError(err error) bool {