Bump tslint from 5.19.0 to 5.20.0 (#2180)

Bumps [tslint](https://github.com/palantir/tslint) from 5.19.0 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@5.19.0...5.20.0)

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

Author: dependabot-preview[bot]

package-lock.json

@@ -56,7 +56,7 @@
     "mocha-junit-reporter": "~1.23.1",
     "mocha-multi-reporters": "~1.1.7",
     "rewire": "~4.0.1",
-    "tslint": "~5.19.0",
+    "tslint": "~5.20.0",
     "typescript": "~3.5.3",
     "vsce": "~1.66.0",
     "vscode": "~1.1.36"