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

script/linux

@@ -2,9 +2,6 @@
 
 set -ex
 
-# Install our submodule dependencies
-git submodule update --init --recursive
-
 # install the wasm toolchain
 which rustup > /dev/null 2>&1 || curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y