Menu/ToC: harmonize font sizes (#7795)

Menu: display the right item ("mandatory") with a
smaller font size related to the left item font size,
instead of a function of perpage.
ToC popups: use same font size as in ToC.

frontend/apps/reader/modules/readertoc.lua

@@ -760,6 +760,7 @@ function ReaderToc:onShowToc()
             alignment = "center",
             show_icon = false,
             text = trimmed_text,
+            face = Font:getFace("infofont", self.items_font_size),
         }
         UIManager:show(infomessage)
         return true