Typo in braininvaders.py: Replace shutil.copy_tree with shutil.copytree

[kbegany]

Fix typo: Replace shutil.copy_tree with shutil.copytree
(See https://docs.python.org/3/library/shutil.html#shutil.copytree)

moabb/moabb/datasets/braininvaders.py

Line 287 in 2a9cf4f

shutil.copy_tree(path_zip.strip(".zip"), directory)

[bruAristimunha]

Many thanks for report!