fix(@angular-devkit/build-optimizer): update typescript to 3.1.5

Fix #12773

Author: filipesilva

packages/angular_devkit/build_optimizer/package.json

@@ -10,7 +10,7 @@
   "dependencies": {
     "loader-utils": "1.1.0",
     "source-map": "0.5.6",
-    "typescript": "3.1.3",
+    "typescript": "3.1.5",
     "webpack-sources": "1.2.0"
   }
 }