Update Freetype 2.13.1 for Qt 5.15.15

We need to make sure all security critical 3rd party modules (https://wiki.qt.io/Third_Party_Code_in_Qt) are the latest one before we can release. It seems Freetype needs an update; we are using 2.13.0 but 2.13.1 is already available;

https://gitlab.freedesktop.org/freetype/freetype/-/tags

Next release where this update is needed is Qt 5.15.15. This should be merged to tqtc/lts-5.15.15 by 31st of July. Please Pick-to: 5.15. 5.15.15