edk2: update submodule to edk2-stable202308

New stable release was tagged in August 2023,
update the edk2 submodule to it.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

edk2 @ 819cfc6b

-Subproject commit f80f052277c88a67c55e107b550f504eeea947d3
+Subproject commit 819cfc6b42a68790a23509e4fcc58ceb70e1965e