Although the HTTP Version appears as a header inside `env`, it's not actually a regular header. When `extract_http_request_headers` is called, it translates the `HTTP_VERSION` "header" into a `Version` header. `Version` is only a provisionally-supported header name, and is semantically meant to represent the version of an (evolving object)[https://www.w3.org/Protocols/HTTP/Object_Headers.html#z13]. It's not correct to pass the HTTP Version as the contents of the `Version` header, so this change skips the processing of that particular header entirely.
Fixing the two warnings listed bellow:
- DEPRECATION WARNING: env is deprecated and will be removed from Rails 5.1
- DEPRECATION WARNING: `render :text` is deprecated because it does not
actually render a `text/plain` response. Switch to `render plain: 'plain
text'` to render as `text/plain`, `render html: '<strong>HTML</strong>'` to
render as `text/html`, or `render body: 'raw'` to match the deprecated
behavior and render with the default Content-Type, which is `text/plain`.