Bump npm from 6.9.0 to 6.13.4 (#493)

Bumps [npm](https://github.com/npm/cli) from 6.9.0 to 6.13.4.
- [Release notes](https://github.com/npm/cli/releases)
- [Changelog](https://github.com/npm/cli/blob/latest/CHANGELOG.md)
- [Commits](npm/cli@v6.9.0...v6.13.4)

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

package.json

@@ -71,7 +71,7 @@
     "mongoose": "^5.3.12",
     "mysql": "^2.16.0",
     "node-gyp": "^3.8.0",
-    "npm": "^6.9.0",
+    "npm": "^6.13.4",
     "oracledb": "^3.1.2",
     "passport": "^0.4.0",
     "passport-google-oauth": "^1.0.0",