Remove AR hook to set the default subgroup_creation_level

app/models/group.rb

@@ -58,8 +58,6 @@ class Group < Namespace
 
   add_authentication_token_field :runners_token, encrypted: -> { Feature.enabled?(:groups_tokens_optional_encryption, default_enabled: true) ? :optional : :required }
 
-  before_create :default_subgroup_creation_level_to_maintainers
-
   after_create :post_create_hook
   after_destroy :post_destroy_hook
   after_save :update_two_factor_requirement
@@ -447,8 +445,4 @@ class Group < Namespace
 
     errors.add(:visibility_level, "#{visibility} is not allowed since there are sub-groups with higher visibility.")
   end
-
-  def default_subgroup_creation_level_to_maintainers
-    self.subgroup_creation_level = ::Gitlab::Access::MAINTAINER_SUBGROUP_ACCESS
-  end
 end