Fix for T85517
Bug: Couldn't type space while holding down the shift key in text spaces (e.g. when saving a file, changing the name of object).
Changes: Removing the key combination of Shift + space in `WM_event_is_ime_switch` method.
Reviewed By: harley, mont29
Maniphest Tasks: T85517
Differential Revision: https://developer.blender.org/D10452