SpringBoot Correct references to Jetty's HTTP2 server module

Update documentation to use org.eclipse.jetty.http2:jetty-http2-server for Jetty HTTP2 server support.

All jetty dependencies were updated in https://github.com/spring-projects/spring-boot/issues/36073, this only updates reference documentation and the exception message.

Comment From: gavlyukovskiy

@wilkinsona I've reverted changes to JettyServletWebServerFactory

Comment From: mhalbritter

Thank you!