test: Drop the duplicate line in setup_bootmenu_image()

The mkimage call is done twice. Remove the duplicate.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/py/tests/test_ut.py b/test/py/tests/test_ut.py
index 39aa103..9166c8f 100644
--- a/test/py/tests/test_ut.py
+++ b/test/py/tests/test_ut.py
@@ -208,8 +208,6 @@
             cons, f'echo here {kernel} {symlink}')
         os.symlink(kernel, symlink)
 
-        u_boot_utils.run_and_log(
-            cons, f'mkimage -C none -A arm -T script -d {cmd_fname} {scr_fname}')
         complete = True
 
     except ValueError as exc: