gnu: docker: Disable tests requiring elevated permissions.

* gnu/packages/docker.scm (docker)[arguments]<#:phases>[delete-failing-tests]:
Disable tests requiring elevated permissions.

gnu/packages/docker.scm

@@ -375,6 +375,9 @@ network attachments.")
              (delete-file "daemon/graphdriver/vfs/vfs_test.go")
              ;; Timeouts after 5 min.
              (delete-file "plugin/manager_linux_test.go")
+             ;; Operation not permitted.
+             (delete-file "daemon/graphdriver/overlay/overlay_test.go")
+             (delete-file "daemon/graphdriver/overlay2/overlay_test.go")
              #t))
          (replace 'configure
            (lambda _