Cirrus-CI: Use standard QEMU package

Issues that required qemu-devel or qemu42 have long since been fixed.
This package also includes the UEFI firmware, so stop trying to install
uefi-edk2-qemu-x86_64.

Direct commit to stable/12 as other changes have not been MFCd.

Sponsored by:	The FreeBSD Foundation

.cirrus.yml

@@ -21,7 +21,7 @@ task:
       TARGET: arm64
       TARGET_ARCH: aarch64
   install_script:
-  - pkg install -y qemu-devel uefi-edk2-qemu-x86_64
+  - pkg install -y qemu
   script:
   - make -j$(sysctl -n hw.ncpu) WITHOUT_TOOLCHAIN=yes buildworld buildkernel
 # FAT root fs fails on stable/12: