Adjust mutant ignored methods

The previously ignored part have been moved from
initializer to model_klasses method.

Author: mpraglowski

ruby_event_store-active_record/.mutant.yml

@@ -32,7 +32,7 @@ matcher:
     - RubyEventStore::ActiveRecord::Event.hook_attribute_type
     - RubyEventStore::ActiveRecord::DoubleSerializationDetector
     - RubyEventStore::ActiveRecord::EventRepositoryReader#initialize
-    - RubyEventStore::ActiveRecord::EventRepository#initialize
+    - RubyEventStore::ActiveRecord::EventRepository#model_klasses
     - RubyEventStore::ActiveRecord::EventRepository#json_data_type?
     - RubyEventStore::ActiveRecord::EventRepository#rescue_from_double_json_serialization!
     - RubyEventStore::ActiveRecord::SkipJsonSerialization