Drop the drain check for kubectl > v1.10.0 (#10657)

Older versions are unsupported for a long time.

roles/upgrade/pre-upgrade/tasks/main.yml

@@ -56,23 +56,6 @@
       delegate_to: "{{ groups['kube_control_plane'][0] }}"
       changed_when: true
 
-    - name: Check kubectl version
-      command: "{{ kubectl }} version --client --short"
-      register: kubectl_version
-      delegate_to: "{{ groups['kube_control_plane'][0] }}"
-      run_once: yes
-      changed_when: false
-      when:
-        - drain_nodes
-        - drain_pod_selector
-
-    - name: Ensure minimum version for drain label selector if necessary
-      assert:
-        that: "kubectl_version.stdout.split(' ')[-1] is version('v1.10.0', '>=')"
-      when:
-        - drain_nodes
-        - drain_pod_selector
-
     - name: Drain node
       command: >-
         {{ kubectl }} drain