cmd: Disable go1.23 tlskyber=1 experiment

Compilation with go 1.24 fails with it, since the experiment has ended. We'll reintroduce post quantum soon.

cmd/caddy/main.go

@@ -1,8 +1,3 @@
-// The below line is required to enable post-quantum key agreement in Go 1.23
-// by default without insisting on setting a minimum version of 1.23 in go.mod.
-// See https://github.com/caddyserver/caddy/issues/6540#issuecomment-2313094905
-//go:debug tlskyber=1
-
 // Copyright 2015 Matthew Holt and The Caddy Authors
 //
 // Licensed under the Apache License, Version 2.0 (the "License");