Make DeafultApplyStrategy private

Co-authored-by: Paweł Pacana <pawel.pacana@gmail.com>
Co-authored-by: Szymon Fiedler <szymon.fiedler@gmail.com>

Author: 3 people

aggregate_root/lib/aggregate_root/default_apply_strategy.rb

@@ -32,4 +32,5 @@ def missing_handler(aggregate, event_type)
 
     attr_reader :strict, :on_methods
   end
+  private_constant :DefaultApplyStrategy
 end