Remove marking LAST_UPDATED dirty since it is now resolved via snapshot check

Author: codeconsole

grails-data-mongodb/core/src/main/groovy/org/grails/datastore/mapping/mongo/engine/codecs/PersistentEntityCodec.groovy

@@ -64,7 +64,6 @@ import org.grails.datastore.mapping.engine.internal.MappingUtils
 import org.grails.datastore.mapping.model.EmbeddedPersistentEntity
 import org.grails.datastore.mapping.model.PersistentEntity
 import org.grails.datastore.mapping.model.PersistentProperty
-import org.grails.datastore.mapping.model.config.GormProperties
 import org.grails.datastore.mapping.model.types.Association
 import org.grails.datastore.mapping.model.types.Embedded
 import org.grails.datastore.mapping.model.types.EmbeddedCollection
@@ -249,12 +248,6 @@ class PersistentEntityCodec extends BsonPersistentEntityCodec {
                 }
 
             }
-            else {
-                // schedule lastUpdated if necessary
-                if (entity.getPropertyByName(GormProperties.LAST_UPDATED) != null) {
-                    dirtyProperties.add(GormProperties.LAST_UPDATED)
-                }
-            }
 
             for (propertyName in dirtyProperties) {
                 def prop = entity.getPropertyByName(propertyName)