Use git recursive option to get submodules

Needed to fully clone a worker that uses a git submodule (like we want to do for tesseract to include remote open source models).

@schneider-y is working on https://gitlab.com/teklia/workers/tesseract/-/merge_requests/24 that includes a submodule.

The docker build is valid, as long as the submodule is cloned (OK on CI), but KO on preprod builds.