Update dependency typescript to v3.9.6

Author: renovate-bot

package.json

@@ -36,7 +36,7 @@
     "jest": "24.7.1",
     "prettier": "1.19.1",
     "ts-jest": "24.3.0",
-    "typescript": "3.9.2"
+    "typescript": "3.9.6"
   },
   "jest": {
     "transform": {