chore(package): update @types/jest to version 24.0.21

Closes #62

Author: greenkeeper[bot]

package.json

@@ -15,7 +15,7 @@
     "watch": "yarn jest --watch"
   },
   "devDependencies": {
-    "@types/jest": "24.0.11",
+    "@types/jest": "24.0.21",
     "@unional/devpkg-node": "^1.2.5",
     "jest": "^24.7.1",
     "jest-junit": "^6.3.0",