chore: refactor npm outdated export

lib/outdated.js

@@ -13,12 +13,14 @@ const Arborist = require('@npmcli/arborist')
 
 const npm = require('./npm.js')
 const output = require('./utils/output.js')
+const usageUtil = require('./utils/usage.js')
 const ansiTrim = require('./utils/ansi-trim.js')
 
-cmd.usage = 'npm outdated [[<@scope>/]<pkg> ...]'
-cmd.completion = require('./utils/completion/installed-deep.js')
+const usage = usageUtil('outdated',
+  'npm outdated [[<@scope>/]<pkg> ...]'
+)
+const completion = (cb) => cb(null, [])
 
-module.exports = cmd
 function cmd (args, cb) {
   outdated(args, cb)
     .then(() => cb())
@@ -267,3 +269,5 @@ function makeJSON (list, opts) {
   })
   return JSON.stringify(out, null, 2)
 }
+
+module.exports =  Object.assign(cmd, { completion, usage })