xhtml_style: drop useless CachingMethod

This function have evolved to something very trivial not accessing anything from database, so caching this no longer really makes sense, also the cache keys are really big.

On a quick benchmark of calling ERP5Site_getTabList 10000 times:
with cache: ERP5Site_getTabList took 12.961781
without cache: ERP5Site_getTabList took 5.395873

product/ERP5/bootstrap/erp5_xhtml_style/SkinTemplateItem/portal_skins/erp5_access_tab/ERP5Site_getTabList.py

-from Products.ERP5Type.Cache import CachingMethod
-
 def getTabList(status_dict, info_dict, add_all_tabs):
   tab_list = []
   basic_mode = status_dict.get('basic_mode', 1)
@@ -68,10 +66,6 @@ if not add_all_tabs:
   status_dict = context.ERP5Site_getConfiguredStatusDict()
   info_dict = context.ERP5Site_getCategorizedModuleActionInformationDict()
 
-getTabList = CachingMethod(getTabList, \
-                           id = 'ERP5Site_getTabListInternal', \
-                           cache_factory = 'erp5_ui_long')
-
 return getTabList(status_dict = status_dict, \
                   info_dict = info_dict, \
                   add_all_tabs = add_all_tabs)