Fix tests relying on lazy-loaded images

These tests can be flaky because it is possible that the image hasn't
been lazy-loaded when we read its `src` attribute.

ee/spec/features/epics/update_epic_spec.rb

@@ -114,7 +114,7 @@ RSpec.describe 'Update Epic', :js do
       end
 
       it 'uploads a file when dragging into textarea' do
-        link_css = 'a.no-attachment-icon img[alt="banana_sample"]'
+        link_css = 'a.no-attachment-icon img.js-lazy-loaded[alt="banana_sample"]'
         link_match = %r{/groups/#{Regexp.escape(group.full_path)}/-/uploads/\h{32}/banana_sample\.gif\z}
         dropzone_file Rails.root.join('spec', 'fixtures', 'banana_sample.gif')
 

spec/features/projects/snippets/create_snippet_spec.rb

@@ -62,7 +62,7 @@ RSpec.describe 'Projects > Snippets > Create Snippet', :js do
     click_button('Create snippet')
     wait_for_requests
 
-    link = find('a.no-attachment-icon img[alt="banana_sample"]')['src']
+    link = find('a.no-attachment-icon img.js-lazy-loaded[alt="banana_sample"]')['src']
     expect(link).to match(%r{/#{Regexp.escape(project.full_path)}/uploads/\h{32}/banana_sample\.gif\z})
   end
 

spec/features/uploads/user_uploads_file_to_note_spec.rb

@@ -78,7 +78,7 @@ RSpec.describe 'User uploads file to note' do
       click_button 'Comment'
       wait_for_requests
 
-      expect(find('a.no-attachment-icon img[alt="dk"]')['src'])
+      expect(find('a.no-attachment-icon img.js-lazy-loaded[alt="dk"]')['src'])
         .to match(%r{/#{project.full_path}/uploads/\h{32}/dk\.png$})
     end
   end