Docs: make http2 configuration more clear

In our configuration guide, we have a section 16.11. Configuring HTTP/2. There are steps how to enable HTTP2 using OpenSSL provider for EAP.

Almost at the end of the section, we have following text:

For more information on the HTTPS listener and configuring Undertow to use HTTPS for web applications, see the Setting Up SSL/TLS for Applications section of How to Configure Server Security.

This is just fine, although I believe such information might be useful for a customer also a little bit earlier. I propose to move this bit of information somewhere right below this part:

To configure Undertow to use HTTP/2, enable the HTTPS listener in Undertow to use HTTP/2 by setting the enable-http2 attribute to true:

/subsystem=undertow/server=default-server/https-listener=https:write-attribute(name=enable-http2,value=true)

You can move it there e.g. as a note with slightly updated content to better fit new position in the text.

Also, please update the reference link of Setting Up SSL/TLS for Applications. Currently it points to some old path:

https://access.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/7.1/html-single/how_to_configure_server_security/#setting_up_an_ssl_tls_for_applications

but correct new path is following:

https://access.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/7.1/html-single/how_to_configure_server_security/#configure_one_way_and_two_way_ssl_tls_for_application