Update last-updated on diff Kep

Author: Antoine Pelisse

keps/sig-cli/20200115-kubectl-diff.md

@@ -12,7 +12,7 @@ approvers:
   - TBD
 editor: TBD
 creation-date: 2020-01-15
-last-updated: 2020-01-27
+last-updated: 2020-03-23
 status: implemented
 see-also:
   - "/keps/sig-api-machinery/0015-dry-run.md"