Remove useless require 'file_size_validator' causing warnings

Signed-off-by: Rémy Coutable <remy@rymai.me>

app/models/group.rb

@@ -15,7 +15,6 @@
 #
 
 require 'carrierwave/orm/activerecord'
-require 'file_size_validator'
 
 class Group < Namespace
   include Gitlab::ConfigHelper

app/models/issue.rb

@@ -20,7 +20,6 @@
 #
 
 require 'carrierwave/orm/activerecord'
-require 'file_size_validator'
 
 class Issue < ActiveRecord::Base
   include InternalId

app/models/note.rb

@@ -20,7 +20,6 @@
 #
 
 require 'carrierwave/orm/activerecord'
-require 'file_size_validator'
 
 class Note < ActiveRecord::Base
   include Gitlab::CurrentSettings

app/models/project.rb

@@ -40,7 +40,6 @@
 #
 
 require 'carrierwave/orm/activerecord'
-require 'file_size_validator'
 
 class Project < ActiveRecord::Base
   include Gitlab::ConfigHelper

app/models/project_import_data.rb

@@ -8,7 +8,6 @@
 #
 
 require 'carrierwave/orm/activerecord'
-require 'file_size_validator'
 
 class ProjectImportData < ActiveRecord::Base
   belongs_to :project

app/models/user.rb

@@ -63,7 +63,6 @@
 #
 
 require 'carrierwave/orm/activerecord'
-require 'file_size_validator'
 
 class User < ActiveRecord::Base
   extend Gitlab::ConfigHelper