Don't use Rails.root.join for upload fixture paths

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

spec/controllers/uploads_controller_spec.rb

@@ -562,7 +562,7 @@ describe UploadsController do
     end
 
     context 'original filename or a version filename must match' do
-      let!(:appearance) { create :appearance, favicon: fixture_file_upload(Rails.root.join('spec/fixtures/dk.png'), 'image/png') }
+      let!(:appearance) { create :appearance, favicon: fixture_file_upload('spec/fixtures/dk.png', 'image/png') }
 
       context 'has a valid filename on the original file' do
         it 'successfully returns the file' do

spec/lib/gitlab/favicon_spec.rb

@@ -18,7 +18,7 @@ RSpec.describe Gitlab::Favicon, :request_store do
     end
 
     it 'uses the custom favicon if a favicon appearance is present' do
-      create :appearance, favicon: fixture_file_upload(Rails.root.join('spec/fixtures/dk.png'))
+      create :appearance, favicon: fixture_file_upload('spec/fixtures/dk.png')
       expect(described_class.main).to match %r{/uploads/-/system/appearance/favicon/\d+/favicon_main_dk.png}
     end
   end

spec/models/project_services/jira_service_spec.rb

@@ -475,7 +475,7 @@ describe JiraService do
     end
 
     it 'includes returns the custom favicon' do
-      create :appearance, favicon: fixture_file_upload(Rails.root.join('spec/fixtures/dk.png'))
+      create :appearance, favicon: fixture_file_upload('spec/fixtures/dk.png')
 
       props = described_class.new.send(:build_remote_link_props, url: 'http://example.com', title: 'title')
       expect(props[:object][:icon][:url16x16]).to match %r{^http://localhost/uploads/-/system/appearance/favicon/\d+/favicon_main_dk.png$}

spec/uploaders/favicon_uploader_spec.rb

@@ -10,7 +10,7 @@ RSpec.describe FaviconUploader do
   end
 
   def upload_fixture(filename)
-    fixture_file_upload(Rails.root.join('spec', 'fixtures', filename))
+    fixture_file_upload("spec/fixtures/#{filename}")
   end
 
   context 'versions' do