build: remove post-processing of .d.ts files (#13294)

Note that the duplication in tsconfig.json files will be fixed in a followup CL now that we have tsconfig inheritance

BREAKING CHANGE: Angular 4 will support only TypeScript 2.1, so we no longer provide backwards compatibility to TS 1.8.

modules/@angular/forms/tsconfig-build.json

@@ -20,7 +20,9 @@
     "inlineSources": true,
     "target": "es5",
     "skipLibCheck": true,
-    "lib": ["es2015", "dom"]
+    "lib": ["es2015", "dom"],
+    // don't auto-discover @types/node, it results in a ///<reference in the .d.ts output
+    "types": []
   },
   "files": [
     "index.ts",