docs: Replace some mentions of jj co with jj new.
#1165
| Job | Run time |
|---|---|
| 5m 15s | |
| 5m 11s | |
| 10m 26s |
jj co with jj new.
#1165
| Job | Run time |
|---|---|
| 5m 15s | |
| 5m 11s | |
| 10m 26s |