[mypy] Fix type annotations for binary tree traversals in data structures (#5556)

* [mypy] Fix type annotations for binary tree traversals in data structures

* Change variable name and update level_order_1 to use a deque

Using a deque instead of a list here, because since we are removing from the beginning of the list, the deque will be more efficient.

* remove duplicate function

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: John Law <johnlaw.po@gmail.com>

* fix function name at line 137

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: John Law <johnlaw.po@gmail.com>

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: John Law <johnlaw.po@gmail.com>

* Remove type alias and use the new syntax

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: John Law <johnlaw.po@gmail.com>

* Remove prints inside functions and return lists

Co-authored-by: John Law <johnlaw.po@gmail.com>