Bump commander from 6.1.0 to 6.2.0

Bumps [commander](https://github.com/tj/commander.js) from 6.1.0 to 6.2.0.
- [Release notes](https://github.com/tj/commander.js/releases)
- [Changelog](https://github.com/tj/commander.js/blob/master/CHANGELOG.md)
- [Commits](tj/commander.js@v6.1.0...v6.2.0)

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -9,7 +9,7 @@
     "url": "https://github.com/jupyterhub/configurable-http-proxy.git"
   },
   "dependencies": {
-    "commander": "~6.1.0",
+    "commander": "~6.2.0",
     "http-proxy": "^1.18.1",
     "lynx": "^0.2.0",
     "strftime": "~0.10.0",