conventions.md: note preference of [[ and [ over test
#1346
| Job | Run time |
|---|---|
| 4m 41s | |
| 1s | |
| 4m 40s | |
| 4m 29s | |
| 4m 40s | |
| 4m 30s | |
| 4m 39s | |
| 4m 41s | |
| 4m 30s | |
| 4m 40s | |
| 4m 41s | |
| 4m 29s | |
| 1s | |
| 4m 41s | |
| 4m 30s | |
| 4m 42s | |
| 4m 29s | |
| 4m 41s | |
| 4m 31s | |
| 1h 18m 16s |