[libpng] remove broken patch

[cenit]

No description provided.

[NancyLi1013]

Hi @cenit, I see that qt5-3d failed on x86-windows from the current CI system.
The error likes this:
CMake Error at scripts/cmake/vcpkg_execute_required_process.cmake:56 (message):
Command failed: C:/vsts/_work/2/s/downloads/tools/jom/jom-1.1.3/jom.exe
Working Directory: C:/vsts/_work/2/s/buildtrees/qt5-3d/x86-windows-rel
Error code: 2
See logs for more information:
C:\vsts_work\2\s\buildtrees\qt5-3d\package-build-x86-windows-rel-out.log
C:\vsts_work\2\s\buildtrees\qt5-3d\package-build-x86-windows-rel-err.log
failureLogs.zip

[cenit]

This one is really curious, I will investigate it soon (I didn’t open the zip as of now): this PR technically should not change anything, since it adds “unused” targets (make the port more future-proof) and removes a patch that was impossible to apply because it was broken with recent sources... I was expecting an “easy” green mark!

[vicroms]

@cenit were you able to get a repro?
I was unable to get one locally.

[cenit]

@vicroms No sorry. Too much busy