[protocol] Update the "OwnableUpgradeable" contract to conform to the latest OpenZeppelin implementation

[PaulRBerg]

In 4c1b47d, we upgraded to v4.5.2 of the @openzeppelin/contracts-upgradeable package. A version which brought a change to the way the initializer modifier works:

• https://unpkg.com/@openzeppelin/contracts-upgradeable@4.3.1/proxy/utils/Initializable.sol
• https://unpkg.com/@openzeppelin/contracts-upgradeable@4.5.2/proxy/utils/Initializable.sol

[PaulRBerg]

Fixed by ce70409 and 86ccdbb.