Bump tslint from 5.16.0 to 5.20.0 (#4487)

Bumps [tslint](https://github.com/palantir/tslint) from 5.16.0 to 5.20.0.
- [Release notes](https://github.com/palantir/tslint/releases)
- [Changelog](https://github.com/palantir/tslint/blob/master/CHANGELOG.md)
- [Commits](palantir/tslint@5.16.0...5.20.0)

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

package.json

@@ -184,7 +184,7 @@
     "tar": "5.0.2",
     "through2": "3.0.1",
     "ts-node": "8.4.0",
-    "tslint": "5.16.0",
+    "tslint": "5.20.0",
     "typescript": "3.4.5",
     "wait-on": "3.2.0",
     "webpack-dev-server": "3.9.0"