To remove a submodule you need to:
git submodule deinit <path_to_submodule>
git rm <path_to_submodule>
git commit -m "Removed submodule"
rm -rf .git/modules/<path_to_submodule>
To remove a submodule you need to:
git submodule deinit <path_to_submodule>
git rm <path_to_submodule>
git commit -m "Removed submodule"
rm -rf .git/modules/<path_to_submodule>