Revert "Reset primary_server when remove_server"

This reverts commit 2948d3bd2e78b5b9110454a7135a81c3fecb2575.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65242 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/drb/drb.rb

@@ -1866,11 +1866,6 @@ module DRb
   # Removes +server+ from the list of registered servers.
   def remove_server(server)
     @server.delete(server.uri)
-    mutex.synchronize do
-      if @primary_server == server
-        @primary_server = nil
-      end
-    end
   end
   module_function :remove_server