fix: use correct disk percentage (#305)

This was the original value. It was changed in ad6d3f2 because
(according to commit message) precentage stopped working. Now, it seems
to be working again.

themes/multicolor/theme.lua

@@ -130,7 +130,7 @@ local fsicon = wibox.widget.imagebox(theme.widget_fs)
 theme.fs = lain.widget.fs({
     notification_preset = { font = "Terminus 10", fg = theme.fg_normal },
     settings  = function()
-        widget:set_markup(markup.fontfg(theme.font, "#80d9d8", string.format("%.1f", fs_now["/"].used) .. "% "))
+        widget:set_markup(markup.fontfg(theme.font, "#80d9d8", string.format("%.1f", fs_now["/"].percentage) .. "% "))
     end
 })
 --]]