Enable snap sync by default

[ligi]

blockers:

• ship snapshots
• Failing to unregister sync peer (which not registered) #22077
• Snap sync crash #22172
• eth/protocols/snap: snap sync testing #22179
• wait for enough peers to support it (by berlin everyone should have that)

[xanoni]

Think this can be closed. Snap is default now.

(however, some trouble with it: #23228)