temp/qemu: remove

The package was originally added with jemalloc to work around a deadlock while compiling mesa. I've tested compiling the mesa-git package on x86_64 for armhf and armv7 and it worked fine. Looking at the original issue report, the problem only happened with the autotools build system and not with meson - and as all our mesa or networkmanager aports are using meson now, I think we can delete this.