Activate HTTP2 (h2c) for studio-client container

With this change, the nginx webserver serving the static files of the studio-client application, will accept only http2 requests. In order to accept HTTP/1.1 you need to set the environment variable PROTOCOL to an emtpy value.

Follow Section, “Activate HTTP2 (h2c) for studio-client container” for upgrade information.

(CMS-13480)