Upgrade untwine to 1.4.0

[uclaros]

Description

Pulling bug fixes and improvements from the latest untwine release:
https://github.com/hobuinc/untwine/releases/tag/1.4.0

[github-actions]

🪟 Windows builds

Download Windows builds of this PR for testing.
Debug symbols for this build are available here.
(Built from commit 49b198e)

[m-kuhn]

This introduced an include problem on Windows, see #59148

D:\a\QGIS\QGIS\external\untwine\untwine\windows\stringconv.hpp(5): fatal error C1083: Cannot open include file: 'untwine/FatalError.hpp': No such file or directory

This include cannot work, the header is in ./external/untwine/untwine/[platform]/stringconv.hpp, not sure how to best solve this. (Well, ideally I would like to see untwine unvendored and consumed as a proper CMake target, but I am not sure that's on any roadmap)

[m-kuhn]

Sorry, previous assessment was wrong, it's obviously about including untwine/FatalError.hpp which boils down to a missing include dir which is more straightforward to fix.