Remove couch_db_plugin from couch_db_epi services

It was replaced by fabric2_db_plugin
diff --git a/src/couch/src/couch_db_epi.erl b/src/couch/src/couch_db_epi.erl
index 21879f6..bfd435a 100644
--- a/src/couch/src/couch_db_epi.erl
+++ b/src/couch/src/couch_db_epi.erl
@@ -35,7 +35,6 @@
 
 services() ->
     [
-        {couch_db, couch_db_plugin},
         {feature_flags, couch_flags}
     ].