ci/vkd3d: drop duplicate submodule update

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39670>

.gitlab-ci/container/build-vkd3d-proton.sh

@@ -28,7 +28,6 @@ git clone https://github.com/HansKristian-Work/vkd3d-proton.git --single-branch
 pushd "$VKD3D_PROTON_SRC_DIR"
 git checkout "$VKD3D_PROTON_COMMIT"
 git submodule update --init --recursive
-git submodule update --recursive
 
 meson setup                                           \
       -D c_args=-Wno-error=incompatible-pointer-types \