doc: pytest: Document the test_bootmenu test

Add this test to the documentation. There was already a function comment
that included the argument, so convert it to the right style to be
rendered correctly in output.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

test/py/tests/test_bootmenu.py

@@ -8,9 +8,9 @@ import pytest
 def test_bootmenu(ubman):
     """Test bootmenu
 
-    ubman -- U-Boot console
+    Args:
+        ubman: U-Boot console
     """
-
     with ubman.temporary_timeout(500):
         ubman.run_command('setenv bootmenu_default 1')
         ubman.run_command('setenv bootmenu_0 test 1=echo ok 1')