Prop 507: Set governance proposal_cancel_ratio to 1

This proposal sets the x/gov parameter proposal_cancel_ratio from 0.5 to 1.0. All other governance parameters remain unchanged.

Currently, a proposer can cancel their own proposal during the voting period and recover half of the deposit. An attacker can exploit this by cancelling a proposal when it is heading toward a NoWithVeto outcome, avoiding the full deposit burn that a veto would trigger. Raising the ratio to 1.0 removes this incentive, because cancelling would then forfeit the entire deposit.

A proposer who believes their proposal is incorrect should not cancel it. Instead, they should ask voters to vote No, which returns the deposit.