bip155: Fix comments URL

Author: laanwj

bip-0155.mediawiki

@@ -4,7 +4,7 @@
   Title: addrv2 message
   Author: Wladimir J. van der Laan <[email protected]>
   Comments-Summary: No comments yet.
-  Comments-URI: 
+  Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0155
   Status: Draft
   Type: Standards Track
   Created: 2019-02-27