Add auction winner check in collectAuctionTokens in EnglishAuctionsLogic.sol

[goldnite]

There was no check for _msgSender() in collectionAuctionTokens.
I have changed following line to check if the _msgSender() is auction winner.
_winningBid.bidder != address(0) is not necessary because _msgSender() cannot be zero address.

• original code

require(_winningBid.bidder != address(0), "Marketplace: no bids were made.");

• suggested code

require(_winningBid.bidder == _msgSender(), "Marketplace: not auction winner.");

I have also changed term winning bidder to auction winner in the marketplace-v3.md.