Update typescript requirement to ~2.7.2 (#9522)

Updates the requirements on [typescript](https://github.com/Microsoft/TypeScript) to permit the latest version.
- [Release notes](https://github.com/Microsoft/TypeScript/releases)
- [Commits](https://github.com/Microsoft/TypeScript/commits/v2.7.2)

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

package.json

@@ -161,7 +161,7 @@
     "scrollama": "^1.4.1",
     "stylelint": "^9.1.1",
     "stylelint-config-standard": "^18.0.0",
-    "typescript": "~2.6.1",
+    "typescript": "~2.7.2",
     "unified": "^6.1.5",
     "values.js": "^1.0.3",
     "xhr2": "^0.1.3"