Use default sshd_config from bookworm.

There is no need to override the settings after all, as the
sshd_config.d settings take precendence, see:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1014234#10

Verified that this is true with "sudo sshd -T".

It is a bit counter-intuitive, but it works!

hosts/common/etc/ssh/sshd_config

@@ -87,8 +87,7 @@ UsePAM yes
 #AllowAgentForwarding yes
 #AllowTcpForwarding yes
 #GatewayPorts no
-# Commented out X11Forwarding to disable it: https://bugs.debian.org/1063488
-#X11Forwarding no
+X11Forwarding yes
 #X11DisplayOffset 10
 #X11UseLocalhost yes
 #PermitTTY yes