AUCTION_PRICE macro does not work on AMP/mobile pages that use nurl

[dgirardi]

Describe the bug

There is an inconsistency between AMP/mobile and "normal" pages when expanding the AUCTION_PRICE macro.

• Prebid expands it on both ad markup and ad URL: https://github.com/prebid/Prebid.js/blob/f407e47f96f12834bd79092bc1b5bd0203967598/src/prebid.js#L506-L507

• on AMP (or other scenarios where PBS cache sources the ad), PUC will only replace it on ad markup:

  prebid-universal-creative/src/renderingManager.js

  Lines 225 to 232 in 68d81fc

  	if(auctionPrice) { // replace ${AUCTION_PRICE} macro with the bidObject.price or hb_pb.
  	bidObject.adm = bidObject.adm.replace('${AUCTION_PRICE}', auctionPrice);
  	} else {
  	/*
  	From OpenRTB spec 2.5: If the source value is an optional parameter that was not specified, the macro will simply be removed (i.e., replaced with a zero-length string).
  	*/
  	bidObject.adm = bidObject.adm.replace('${AUCTION_PRICE}', '');
  	}