Revert "Use TS 2.2 to build VSCode (#24734)"

This reverts commit f3653925.

build/monaco/package.json

@@ -48,7 +48,7 @@
     "sinon": "^1.17.2",
     "source-map": "^0.4.4",
     "tslint": "^4.3.1",
-    "typescript": "2.2.2",
+    "typescript": "2.1.5",
     "typescript-formatter": "4.0.1",
     "underscore": "^1.8.2",
     "vinyl": "^0.4.5",

package.json

@@ -100,7 +100,7 @@
     "sinon": "^1.17.2",
     "source-map": "^0.4.4",
     "tslint": "^4.3.1",
-    "typescript": "2.2.2",
+    "typescript": "2.1.5",
     "typescript-formatter": "4.0.1",
     "uglify-js": "2.4.8",
     "underscore": "^1.8.2",