feat(submodule): add deinit method to Submodule (#2014)#2129

mvanhorn wants to merge 2 commits intogitpython-developers:maingitpython-developers/GitPython:mainfrom

mvanhorn:feat/2014-submodule-deinitmvanhorn/GitPython:feat/2014-submodule-deinitCopy head branch name to clipboard