Update dependency typescript to v4

Author: renovate-bot

appengine/typescript/package.json

@@ -20,14 +20,14 @@
   },
   "dependencies": {
     "express": "^4.16.3",
-    "typescript": "^3.0.1"
+    "typescript": "^4.0.0"
   },
   "devDependencies": {
     "mocha": "^8.0.0",
     "wait-port": "^0.2.7",
     "@types/express": "^4.16.0",
     "chai": "^4.2.0",
     "tslint": "^6.0.0",
-    "typescript": "^3.8.3"
+    "typescript": "^4.0.0"
   }
 }

package.json

@@ -26,6 +26,6 @@
     "gts": "^2.0.0",
     "prettier": "^2.0.0",
     "requestretry": "^4.0.0",
-    "typescript": "^3.8.3"
+    "typescript": "^4.0.0"
   }
 }