Dependencies: Bump npm from 6.9.0 to 6.13.4 (#21095)

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](https://github.com/npm/cli/compare/v6.9.0...v6.13.4)

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

package.json

@@ -109,7 +109,7 @@
     "ng-annotate-webpack-plugin": "0.3.0",
     "ngtemplate-loader": "2.0.1",
     "node-sass": "4.12.0",
-    "npm": "6.9.0",
+    "npm": "6.13.4",
     "optimize-css-assets-webpack-plugin": "5.0.1",
     "phantomjs-prebuilt": "2.1.16",
     "pixelmatch": "4.0.2",