Builds in strict mode fail when lightmapper falls back to CPU

Steps to reproduce:

1. Build in strict mode ensuring that the lightmapper falls back to CPU

2. 

3. 

Actual results: The information about the fallback is logged as an error, failing the build

Expected results: The information about the fallback is logged as a warning, not failing the build

Reproducible with versions: 2022.3, 2021.3

Not reproducible with versions: 2023.3

Can’t test with versions: 

Tested on (OS): 

Notes:

• See https://unity3d.zendesk.com/agent/tickets/1727476.