Do not set parent keymap of magit-todos-section-map

This is not necessary to make the regular magit-status keys work in the TODOs section. In fact, it causes a bug when used with evil-collection, which uses x instead of k for delete (so that k can move the cursor up one line). Setting the parent keymap unnecessarily confuses evil-collection and causes k to attempt to delete the "thing" at point instead of scrolling up.