How to reproduce:
1. Open the attached "URPWebGLBug.zip" project
2. Go to File -> Build And Run
3. Press the "Scene 2 - doesn't work" button in the browser
4. Observe the application (Post Processing and Anti-aliasing set to FXAA)
5. Press the "Back" button
6. Press the "Scene 3 - doesn't work" button in the browser
7. Observe the application (Post Processing disabled and Anti-aliasing set to None)

Expected result: Application is not over-illuminated (step 4 and 7)
Actual result: Application is over-illuminated (step 4 and 7)

Reproducible with: 2021.1.0a1 (10.2.2), 2021.1.0b5 (11.0.0), 2021.2.0a3 (11.0.0)
Not reproducible with: 2019.4.19f1 (7.5.3), 2020.2.3f1 (10.2.2)

Notes:
- The issue seems to disappear when the Library folder is deleted (But users are able to reproduce it even after deleting the Library folder)
- Pressing the "Scene 1 - works" button in the application opens a Scene where only Post Processing is enabled and it's not over-illuminated
- The issue is reproducible with both WebGL 1 and WebGL 2
- The issue is reproducible with both Linear and Gamma Color Space
- The issue is not reproducible in the Editor and Windows Build
- Couldn't reproduce the issue on a fresh project