[2D][SpriteEditor] While sprite editor tab is not in focus, sprite rects will not be updated and causes visual errors

Repro steps:
1. Open attached "SpriteEditorWindow_UpdateBug" project
2. Open BirdHeroSprite in Sprite Editor, change Sprite Mode from Multiple to Single, hit Apply, observe sprite only has 1 sprite rect in Sprite Editor
3. Change Sprite Mode back to Multiple, click on Scene tab so the Sprite Editor is not visible on screen, change Sprite Mode from Multiple to Single again, hit Apply, go back to Sprite Editor tab, observe sprite still has 3 sprite rects

Expected result: Even without the Sprite Editor in focus, sprite rects of sprites should change depending on importer inspector settings
Actual result: Without the Sprite Editor in focus, sprite rects of sprites do not change depending on importer inspector settings