Fixes #32238 - Bind systemd socket to IPv6

By default foreman.socket binds to IPv4 only. This was done to make
matching it in Puma easier, but it's not really what should be done in
2021 where everything should be dual stack by default.

In aecc318 the need for this matching
in Puma was removed which makes it much more flexible. The default
should be updated.

Note that the installer currently always overrides it so it's not really
a difference for most, but I want to modify the installer to rely on the
default.

extras/systemd/foreman.socket

@@ -2,11 +2,7 @@
 Description=Foreman HTTP Server Accept Sockets
 
 [Socket]
-# Note Puma must be configured to listen on the same IP/port. If there's a
-# mismatch, it will bind again. The port can already be in use, for example when
-# systemd is configured with [::]:3000 but Puma with 0.0.0.0:3000. The port is
-# then already in use.
-ListenStream=0.0.0.0:3000
+ListenStream=3000
 
 # Socket options matching Puma defaults
 NoDelay=true