Remove unnecessary user mocks

spec/lib/banzai/filter/gollum_tags_filter_spec.rb

@@ -6,8 +6,7 @@ RSpec.describe Banzai::Filter::GollumTagsFilter do
   include FilterSpecHelper
 
   let(:project) { create(:project) }
-  let(:user) { double }
-  let(:wiki) { ProjectWiki.new(project, user) }
+  let(:wiki) { ProjectWiki.new(project, nil) }
 
   describe 'validation' do
     it 'ensure that a :wiki key exists in context' do

spec/lib/banzai/filter/wiki_link_filter_spec.rb

@@ -7,8 +7,7 @@ RSpec.describe Banzai::Filter::WikiLinkFilter do
 
   let(:namespace) { build_stubbed(:namespace, name: "wiki_link_ns") }
   let(:project)   { build_stubbed(:project, :public, name: "wiki_link_project", namespace: namespace) }
-  let(:user) { double }
-  let(:wiki) { ProjectWiki.new(project, user) }
+  let(:wiki) { ProjectWiki.new(project, nil) }
   let(:repository_upload_folder) { Wikis::CreateAttachmentService::ATTACHMENT_PATH }
 
   it "doesn't rewrite absolute links" do

spec/lib/banzai/pipeline/wiki_pipeline_spec.rb

@@ -5,7 +5,7 @@ require 'spec_helper'
 RSpec.describe Banzai::Pipeline::WikiPipeline do
   let_it_be(:namespace) { create(:namespace, name: "wiki_link_ns") }
   let_it_be(:project)   { create(:project, :public, name: "wiki_link_project", namespace: namespace) }
-  let_it_be(:wiki)      { ProjectWiki.new(project, double(:user)) }
+  let_it_be(:wiki)      { ProjectWiki.new(project, nil) }
   let_it_be(:page)      { build(:wiki_page, wiki: wiki, title: 'nested/twice/start-page') }
 
   describe 'TableOfContents' do