Fix Flow.

Removed `@flow` annotation from files that don't actually pass Flow check at the moment. These will be added back file by file once the files are properly converted to use Flow.

Closes #3064

packages/babel-generator/src/node/index.js

@@ -1,5 +1,3 @@
-/* @flow */
-
 import whitespace from "./whitespace";
 import * as parens from "./parentheses";
 import each from "lodash/collection/each";

packages/babel-generator/src/node/whitespace.js

@@ -1,5 +1,3 @@
-/* @flow */
-
 import isBoolean from "lodash/lang/isBoolean";
 import each from "lodash/collection/each";
 import map from "lodash/collection/map";