Pick up TS 3.1 final

Fixes #58994

extensions/package.json

@@ -3,7 +3,7 @@
   "version": "0.0.1",
   "description": "Dependencies shared by all extensions",
   "dependencies": {
-    "typescript": "3.1.1-insiders.20180926"
+    "typescript": "3.1.1"
   },
   "scripts": {
     "postinstall": "node ./postinstall"

extensions/yarn.lock

@@ -2,6 +2,6 @@
 # yarn lockfile v1
 
 
-typescript@3.1.1-insiders.20180926:
-  version "3.1.1-insiders.20180926"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.1.1-insiders.20180926.tgz#f043ae9bd68ad7f392a6c25d005a623275116866"
+typescript@3.1.1:
+  version "3.1.1"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.1.1.tgz#3362ba9dd1e482ebb2355b02dfe8bcd19a2c7c96"