Bump ERC1967 pragma to 0.8.4

[Amxx]

Fixes #2979

PR Checklist

• Tests
• Documentation
• Changelog entry

[frangio]

I don't really understand, it looks like the current code compiles fine with 0.8.2. Can you confirm that this is necessary?

[Amxx]

In remix, with 0.8.2 selected, I am able to compile

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/proxy/ERC1967/ERC1967Upgrade.sol";

[frangio]

Ok then if I understand correctly this can be closed.