NEWS, man: move description of SR-IOV-R net naming to v255

https://github.com/systemd/systemd/pull/29582 adds the "v254" name. This also
changes what the default is and what "latest" refers to. Without the name, the
code could be enabled via runtime configuration. Nevertheless, it could be
enabled at compilation time. In other words:
  meson setup build -Ddefault-net-naming-scheme=v254
would work, but
  net.naming-scheme=v254
would fail.

It is possible that people were using the compile-time override, so I think
we should allow "v254" scheme to stay and clearly document that it wasn't the
default.

Unfortunately, unless people manually introduced the compile-time override, we
were never actually testing the new code too. So all the pull request testing
was not useful.

NEWS

@@ -60,6 +60,13 @@ CHANGES WITH 255 in spe:
           is now dropped, as it never worked, hence it should not be used by
           anyone.
 
+        * The predictable network interface naming logic is extended to include
+          the SR-IOV-R "representor" information in network interface names.
+          This feature was intended for v254, but even though the code was
+          merged, the part that actually enabled the feature was forgotten.
+          It is now enabled by default and is part of the new "v255" naming
+          scheme.
+
         Changes in systemd-analyze:
 
         * "systemd-analyze plot" has gained tooltips on each unit name with
@@ -576,8 +583,11 @@ CHANGES WITH 254:
           selects the default value of the per-network setting of the same
           name.
 
-        * The predictable network interface naming logic will now include
-          SR-IOV-R "representor" information in network interface names.
+        * The predictable network interface naming logic was extended to
+          include SR-IOV-R "representor" information in network interface
+          names. Unfortunately, this feature was not enabled by default and can
+          only be enabled at compilation time by setting
+          -Ddefault-net-naming-scheme=v254.
 
         * The DHCPv4 + DHCPv6 + IPv6 RA logic in networkd gained support for
           the RFC8910 captive portal option.