K2GO-394 fix(maps): remove the dead is_proot RPC download patch

0003-maps-download-is-proot-rpc.patch is leftover from the abandoned aria2 RPC
approach: it splits the maps download task by is_proot and gives the proot variant
--enable-rpc, which is exactly the flag that wedged aria2 at zero connections (the
reason the approach was dropped). It reached main with the app PR's RPC-era history.

The shipped design downloads base maps through dash-node ahead of the runrole and
leaves the maps role stock -- its native creates: skips the pre-placed files -- so
there is intentionally no maps role patch (see
controller/docs/ADR-K2GO-394-maps-download-via-dashnode.md and the upstream-patches
README). Applying this dead patch in the rootfs bake would re-patch the role with
the retired RPC variant, so remove it.

Author: luisguzman-adfa