Mark BIP 21 as replaced (by BIP 321)

Author: TheBlueMatt

README.mediawiki

@@ -124,7 +124,7 @@ Those proposing changes should consider that ultimately consent may rest with th
 | URI Scheme
 | Nils Schneider, Matt Corallo
 | Standard
-| Final
+| Replaced
 |- style="background-color: #cfffcf"
 | [[bip-0022.mediawiki|22]]
 | API/RPC

bip-0021.mediawiki

@@ -6,11 +6,18 @@
           Matt Corallo <[email protected]>
   Comments-Summary: No comments yet.
   Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0021
-  Status: Final
+  Status: Replaced
   Type: Standards Track
   Created: 2012-01-29
+  Superseded-By: 321
 </pre>
 
+=Superseded by BIP 321=
+
+This BIP has been superseded and replaced with BIP 321. Please see [[bip-0321.mediawiki|BIP 321]] instead.
+
+=Original BIP=
+
 This BIP is a modification of an earlier [[bip-0020.mediawiki|BIP 0020]] by Luke Dashjr. BIP 0020 was based off an earlier document by Nils Schneider. The alternative payment amounts in BIP 0020 have been removed.
 
 ==Abstract==