Remove bootstrap period from contracts

[sajanrajdev]

As decided, we will not launch with a predefined redemption enabling period (bootstraping), instead we will enable redemtpions as we see fit according to predefined TVL and users targets. For this reason, we should remove the hardcoded bootstrap inherited from Liquity: https://github.com/Badger-Finance/ebtc/blob/a0644bf9140dc8ed79d71e24db2b4684e12413a8/packages/contracts/contracts/CdpManager.sol#L354

[sajanrajdev]

#661