Remove ProspectiveParachainsMode usage in backing subsystem
#13756
| Job | Run time |
|---|---|
| 10s | |
| 16s | |
| 15s | |
| 19s | |
| 43s | |
| 1m 2s | |
| 2m 8s | |
| 2m 24s | |
| 1m 2s | |
| 1m 11s | |
| 2m 11s | |
| 1s | |
| 11m 42s |