OvmfPkg: retire "create-release.py"

OvmfPkg: retire "create-release.py"

Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=1653

"create-release.py" generates a 2-BSDL copyright block that will no longer
apply once we fix <https://bugzilla.tianocore.org/show_bug.cgi?id=1373>.

Rather than update "create-release.py", remove it. We haven't used it in
several years now, plus source releases of upstream edk2 are now covered
by the edk2 stable tags
<https://github.com/tianocore/tianocore.github.io/wiki/EDK-II#stable-tags>.

Regarding binary releases of upstream OVMF: OVMF and ArmVirtQemu binaries
built at the edk2 stable tags are being bundled with upstream QEMU,
similarly to other firmware that runs on QEMU platforms:
<https://lists.gnu.org/archive/html/qemu-devel/2019-03/msg06148.html>.
Furthermore, the Xen project has provided its own builds of OVMF and
ArmVirtXen for a good while now.

Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Julien Grall <julien.grall@arm.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Jordan Justen <jordan.l.justen@intel.com>