fix(ping): make "npm ping" echo a right time

There is no need to make the time divided by 1000 because of the time unit 'ms'. 
Currently a typical command and response:
PS C:\projects> npm ping
npm notice PING http://registry.npmjs.org/
npm notice PONG 0.752ms

lib/ping.js

@@ -27,7 +27,7 @@ class Ping extends BaseCommand {
     const start = Date.now()
     const details = await pingUtil(this.npm.flatOptions)
     const time = Date.now() - start
-    log.notice('PONG', `${time / 1000}ms`)
+    log.notice('PONG', `${time}ms`)
     if (this.npm.config.get('json')) {
       this.npm.output(JSON.stringify({
         registry: this.npm.config.get('registry'),