When switching from GLCore to OpenGL2 and some shader functionality doesn’t work, switching back to GLCore won’t make the shader work until a restart or manual reimport of the shader.

Repro steps:
1. Open examples scene from attached project
2. Go to Player settings, uncheck “Auto Graphics API for Mac” and switch the default API to OpenGL2.
3. Observe model in scene view becomes pink and shader errors appear.
4. Switch the API back to OpenGLCore.
5. Observe how the shader in the scene is still not working.

Expected outcome: shader to automatically reimport/update when Graphics API is switched.

Notes:
- Not a regression, tested back to 5.3.0f4 (2524e04062b4)
- restarting or manually reimporting the shader fixes the issue.