How to reproduce:
1. Open the attached project "case_1351651-Project.zip"
2. Import the attached AssetPostprocessor
3. In the Project Window, re-import Sprites
4. Select a re-imported Sprite
5. View it in the Inspector window
6. View it in the Project window

Expected result: Thumbnail in the project window is updated when a sprite is altered
Actual result: Thumbnail in the project window is not updated when a sprite is altered

Reproducible with: 2021.1.0a1, 2021.1.17f1, 2021.2.0b5, 2022.1.0a6
Not reproducible with: 2019.4.29f1, 2020.3.16f1, 2022.1.0a7

Notes:
- Only reproducible with the large icon, small icon shows the correct thumbnail
- Not reproducible with newly imported sprites/textures