HTTPClient dependency

No need to depend on extra-patch version, as far as I know.

2.2 introduced:
```
      * [INCOMPAT] Rename HTTPClient::HTTP::Message#body to #http_body, then
        add #body as an alias of #content. It's incompatible change though
        users rarely depends on this method. (I've never seen such a case)
        Users who are using req.body and/or res.body should follow this
        change. (req.http_body and res.http_body)
```

Didn't see any other incompatibilities.