Promote Draft->Final BIPs: 50 and 73

BIP 50: Proposed action items, including the hardfork, are completed.

BIP 73: Implemented by at least Bitcoin Core and BitPay.

bip-0073.mediawiki

@@ -2,7 +2,7 @@
   BIP: 73
   Title: Use "Accept" header for response type negotiation with Payment Request URLs
   Author: Stephen Pair <stephen@bitpay.com>
-  Status: Draft
+  Status: Final
   Type: Standards Track
   Created: 2013-08-27
 </pre>