Don't start evicting peers right after `SyncingEngine` is started (#14216)

* Don't start evicting peers right after `SyncingEngine` is started

Parachain collators may need to wait to receive a relaychain block before
they can start producing blocks which can cause `SyncingEngine` to
incorrectly evict them.

When `SyncingEngine` is started, wait 2 minutes before the eviction is
activated to give collators a chance to produce a block.

* fix doc

* Use `continue` instead of `break`

* Trigger CI

---------

Co-authored-by: parity-processbot <>