Menu: Enable/Disable the pagination Button properly

Otherwise, the dim state isn't updated properly, because Button trusts the state flag.

Regression since https://github.com/koreader/koreader/commit/6132e8c904c9e019bfd08e6b534306a9decd416d

Fix #7317

frontend/ui/widget/menu.lua

@@ -967,7 +967,7 @@ function Menu:updatePageInfo(select_number)
         -- update page information
         if self.page_num > 1 then
             self.page_info_text:setText(FFIUtil.template(_("Page %1 of %2"), self.page, self.page_num))
-            self.page_info_text.enabled = true
+            self.page_info_text:enable()
         else
             self.page_info_text:setText("");
         end
@@ -984,7 +984,7 @@ function Menu:updatePageInfo(select_number)
         self.page_return_arrow:enableDisable(#self.paths > 0)
     else
         self.page_info_text:setText(_("No choices available"))
-        self.page_info_text.enabled = false
+        self.page_info_text:disable()
     end
 end