Remove ethtool workaround, issue is now fixed (#6579)

tests/testcases/040_check-network-adv.yml

@@ -16,12 +16,6 @@
     netchecker_port: 31081
 
   tasks:
-    - name: Flannel | Disable tx and rx offloading on VXLAN interfaces (see https://github.com/coreos/flannel/pull/1282)
-      command: "ethtool --offload flannel.1 rx off tx off"
-      ignore_errors: true
-      when:
-        - kube_network_plugin|default('calico') == 'flannel'
-
     - name: Force binaries directory for Container Linux by CoreOS and Flatcar
       set_fact:
         bin_dir: "/opt/bin"