src: fix check-imports.py linter errors

This patch fixes all the linter errors.

PR-URL: https://github.com/nodejs/node/pull/6105
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

src/handle_wrap.cc

@@ -9,7 +9,6 @@
 
 namespace node {
 
-using v8::Boolean;
 using v8::Context;
 using v8::FunctionCallbackInfo;
 using v8::HandleScope;