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

src/tokenizer/index.js

@@ -1,5 +1,3 @@
-/* @flow */
-
 import type { TokenType } from "./types";
 import { isIdentifierStart, isIdentifierChar, isKeyword } from "../util/identifier";
 import { types as tt, keywords as keywordTypes } from "./types";

src/tokenizer/state.js

@@ -1,5 +1,3 @@
-/* @flow */
-
 import type { TokContext } from "./context";
 import type { Token } from "./index";
 import { Position } from "../util/location";

src/tokenizer/types.js

@@ -1,5 +1,3 @@
-/* @flow */
-
 // ## Token types
 
 // The assignment of fine-grained, information-carrying type objects