Celostats does not prune validators after validator key is rotated

[jcortejoso]

Expected Behavior

celostats-server should not show as validators nodes whose key have been rotated and they are not any longer the active validator.

Current Behavior

Celostats report as elected validator the new validator with the new active validation key, and the validator with the old authorized key.

Steps to Reproduce Behavior

Have an elected validator with an authorized key. Run a second validator with a new key not elected. Rotate the validator key from the first validator to the new one.