test(menubar): don't try to cover deprecated methods (calling any of them will make the warning-check fail in tests)

lib/menubar/utils.lua

@@ -409,6 +409,8 @@ function utils.parse_dir(dir_path, callback)
     end)
 end
 
+-- luacov: disable
+
 function utils.compute_textbox_width(textbox, s)
     gdebug.deprecate("Use 'width, _ = textbox:get_preferred_size(s)' directly.", {deprecated_in=4})
     s = screen[s or mouse.screen]
@@ -421,6 +423,8 @@ function utils.compute_text_width(text, s, font)
     return w_textbox.get_markup_geometry(text, s, font)['width']
 end
 
+-- luacov: enable
+
 return utils
 
 -- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80