Makefile: remove obsolete edk2 exception from "clean" rule

The file "BaseTools/Source/Python/UPT/Dll/sqlite3.dll" was removed in edk2
commit 26e2b295ec7a ("BaseTools:Remove unused
BaseTools\Source\Python\UPT\Dll", 2019-05-08), part of edk2-stable201905,
so skipping it in the outermost in-tree "clean" rule is unnecessary.

Remove the obsolete pathname reference.

Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugs.launchpad.net/qemu/+bug/1852196


Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200908072939.30178-2-lersek@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>