news: remove kernel version reference from switchdev entry

The functionality was added in 4.8, but due to a rename of
the DEVLINK_CMD_ESWITCH_GET constant in the kernel headers,
the headers from kernel 4.11 are required by the libvirt code.

Remove the reference from the news entry, since it could be
misleading.

docs/news.xml

@@ -56,7 +56,7 @@
         <description>
             Allow querying the NIC interface capabilities for the
             availability of switchdev offloading (also known as
-            kernel-forward-plane-offload introduced in kernel 4.8).
+            kernel-forward-plane-offload).
         </description>
       </change>
     </section>