Remove references to submodules (#11673)

This PR removes the references to initializing Git submodules as part of
building Zed.

These are no longer needed, as our only submodule was removed in #11672.

Release Notes:

- N/A
b34ab6f3a1Marshall Bowers committed on 5/10/2024, 6:33:53 PM· committed by GitHubparentc9738a2
9 files changedLine totals unavailable