[refactor] docker: remove submodules support

[chicco785]

Is your feature request related to a problem? Please describe the problem.

submodules are the evil of modern sw development:

• Detached workflow
• Extra commands / friction
• Merge conflicts & rebases
• Nested submodules = chaos
• Poor discoverability

Describe the solution you'd like

remove support for submodules.

Additional context

No response

[chicco785]

this is a guillaume's legacy. let's evaluate if we can remove it.

[chicco785]

up

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