cleanup: Remove expired mingw32 ports:

2023-11-20 devel/mingw32-libyaml: Last upstream release was in 2014 and mingw32 project is defunct
2023-11-20 devel/mingw32-pdcurses: Last upstream release was in 2009 and mingw32 project is defunct
2023-11-20 devel/mingw32-openssl: Upstream reached EOL and mingw32 project is defunct
2023-11-20 devel/mingw32-pthreads: Last upstream release was in 2012 and mingw32 project is defunct
2023-11-20 devel/mingw32-directx: Last upstream release was in 2002 and mingw32 project is more or less dead
2023-11-20 math/mingw32-libgmp: Broken for more than a year
2023-11-20 devel/mingw32-libffi: Last upstream release was in 2014 and mingw32 project is defunct
2023-11-21 devel/mingw32-bin-msvcrt: Last upstream release was in 2014 and project mingw32 is defunct
2023-11-21 devel/mingw32-zlib: Last upstream release was in 2014 and project mingw32 is defunct
2023-11-21 devel/mingw32-gcc: Upstream release was in 2015 and mingw32 project is defunct