test/wildmode_spec: fix flaky test

a00eb23c27da fixed one race, but not this one:

    [  ERROR   ] test/functional/ui/wildmode_spec.lua @ 84: 'wildmenu' is preserved during :terminal activity
    test/functional/ui/screen.lua:587: Row 1 did not match.
    Expected:
      |*                         |
      |                         |
      |                         |
      |define  jump  list  >    |
      |:sign define^             |
    Actual:
      |*0: !terminal_output!     |
      |                         |
      |                         |
      |define  jump  list  >    |
      |:sign define^             |
    To print the expect() call that would assert the current screen state, use
    screen:snapshot_util(). In case of non-deterministic failures, use
    screen:redraw_debug() to show all intermediate screen states.
    stack traceback:
            test/functional/ui/screen.lua:587: in function '_wait'
            test/functional/ui/screen.lua:370: in function 'expect'
            test/functional/ui/wildmode_spec.lua:22: in function 'expect_stay_unchanged'
            test/functional/ui/wildmode_spec.lua:92: in function <test/functional/ui/wildmode_spec.lua:84>

0 files changed, 0 insertions, 0 deletions