Sync: Fix issue of not freeing a block announcement slot (#8006)

* Sync: Fix issue of not freeing a block announcement slot

There was a bug that when the block announcement validation returned an
error, the slot reserved for this validation wasn't freed. This could
lead to a situation where we rejected any block announcement from such a
peer for that the block announcement returned an error multiple times.

* Better logging

* Fuck I'm dumb

* 🤦