OvmfPkg: drop stale SafeBlockIoLib and SafeOpenProtocolLib resolutions

OvmfPkg: drop stale SafeBlockIoLib and SafeOpenProtocolLib resolutions

These are listed under "ShellPkg/Application/Shell/Shell.inf", but they
have been commented out ever since commit 345a0c8fce38 ("OvmfPkg: Add
support for UEFI shell", 2011-06-26). No such lib classes exist in edk2.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>