consensus: Reduce Maturity to 1 Epoch

[fed-franz]

Summary

Change MATURITY to be 1 EPOCH;

Relevant Context (optional)

After discussing stake maturity with @herr-seppia, we agreed on the following:

• maturity (ie, the period to wait before being eligible) is necessary to allow pre-verify future blocks
• waiting 1 full epoch seems to be sufficient to allow pre-verifying blocks from the following epoch (ie, if I'm in epoch X and I receive a block from epoch X+1, I will be able to know the Provisioner set in that epoch and check block generator and voters are included in the list)