chore(consensus): remove some unnecessary validator metrics

[kpop-dfinity]

1. These metrics are unused
2. They don't track what they are supposed to: the description says Number of (...) shares being validated every block but we never reset the counter so in reality it counts the total number of validated shares
3. They are not accurate: we don't increment the counter when some validations fail (e.g. parent hash mismatch or when random tape height = 0) or we double count some shares when the validation failed due to some transient error