NEWS: mention the sd_varlink_field_type_t breakage

Follow-up for 93d768e0f3. The commit with
the fix didn't mention this, but the reported reproducer was:
> Install openSUSE Tumbleweed with account-utils and systemd v258.
> Compile and install systemd v260. Run "varlinkctl list-methods
> /run/account/newidmapd-socket" -> the newidmap service crashes in
> varlink_idl_format_all_fields(). Recompile newidmap with systemd v260
> headers -> varlinkctl list-methods works again.

Other people might hit the same issue, so let's mention that this was
fixed.

NEWS

@@ -68,12 +68,17 @@ CHANGES WITH 260 in spe:
         * The org.systemd.login1.Manager D-Bus interface has a minor API break.
           The CanPowerOff(), CanReboot(), CanSuspend(), etc. family of methods
           have introduced new return values which may break downstream
-          consumers, such as desktop environments. The new return values more
+          consumers such as desktop environments. The new return values more
           precisely communicate the status of inhibitors: 'inhibited',
           'inhibitor-blocked', and 'challenge-inhibitor-blocked'. This allows
           desktops to differentiate between system administrator policy and
           temporary restrictions imposed by inhibitors.
 
+        * In systemd-260-rc1, the sd_varlink_field_type_t enum was extended in
+          a way that changed the numerical values of existing fields. This was
+          reverted for -rc2. Programs using sd-varlink and compiled with the
+          headers from -rc1 must be recompiled.
+
         New system interfaces and components:
 
         * The os-release(5) gained a new field FANCY_NAME= that is similar to