change bsip#15 status to installed

Author: abitmore

bsip-0015.md

@@ -1,7 +1,7 @@
     BSIP: 13
     Title: Disable negative voting on workers
     Authors: Daniel Larimer <[email protected]>
-    Status: Draft
+    Status: Installed
     Type: Protocol
     Created: 2015-03-09
     Discussion: https://github.com/cryptonomex/graphene/issues/607