Improve schlick_diffuse docstring
#1234
| Job | Run time |
|---|---|
| 3m 16s | |
| 1m 12s | |
| 2m 35s | |
| 1m 13s | |
| 2m 46s | |
| 1m 34s | |
| 2m 41s | |
| 1m 12s | |
| 3m 8s | |
| 1m 15s | |
| 2m 19s | |
| 2m 39s | |
| 2m 44s | |
| 2m 9s | |
| 2m 8s | |
| 4m 52s | |
| 5m 36s | |
| 6m 29s | |
| 5m 15s | |
| 5m 42s | |
| 1m 8s | |
| 1h 1m 53s |