Remove bad couch_db:close/1 call

This is unnecessary as the changes feed loop will do
the necessary database close once it starts waiting
for database update events. Plus, this close call
will fail when the database is deleted - this causes
sporadic replicator_db.js test failures.

src/couch_replicator/src/couch_replicator_manager.erl

@@ -255,8 +255,7 @@ changes_feed_loop() ->
                 (_, _) ->
                     ok
                 end
-            ),
-            couch_db:close(Db)
+            )
         end
     ),
     {Pid, RepDbName}.