The most effective way to remove a git submodule (source):
git submodule deinit <path_to_submodule>
git rm <path_to_submodule>
git commit -m "Removed submodule "
rm -rf .git/modules/<path_to_submodule>
The most effective way to remove a git submodule (source):
git submodule deinit <path_to_submodule>
git rm <path_to_submodule>
git commit -m "Removed submodule "
rm -rf .git/modules/<path_to_submodule>