To remove Counters from the main FleekERC721 contract

[EmperorOrokuSaki]

The only advantage that Counters brings to the contract over basic arithmetic is the checks it does on decrementation. Since the release of Solidity v0.8, the overflow checks have become part of the language itself.
There does not seem to be a reason to keep the library, especially because we don't decrement our counters ever in the contract.

[zoruka]

I'm up to not use it if cleans up the code.

[EmperorOrokuSaki]

Decided to remove it per our discussion on Discord's daily sync.

[EmperorOrokuSaki]

Pull Request: #137

[EmperorOrokuSaki]

Will lock this conversation.

[EmperorOrokuSaki]

Update: Closing the discussion due to inactivity.