Update gitlab_sign_in to sign_in for release tests

This commit updates all release-related feature specs to use
`sign_in` instead of `gitlab_sign_in`.

spec/features/projects/releases/user_creates_release_spec.rb

@@ -18,7 +18,7 @@ RSpec.describe 'User creates release', :js do
 
     project.add_developer(user)
 
-    gitlab_sign_in(user)
+    sign_in(user)
 
     visit new_page_url
 

spec/features/projects/releases/user_views_edit_release_spec.rb

@@ -13,7 +13,7 @@ RSpec.describe 'User edits Release', :js do
 
     project.add_developer(user)
 
-    gitlab_sign_in(user)
+    sign_in(user)
 
     visit edit_project_release_path(project, release)
 

spec/features/projects/releases/user_views_releases_spec.rb

@@ -16,7 +16,7 @@ RSpec.describe 'User views releases', :js do
   shared_examples 'releases page' do
     context('when the user is a maintainer') do
       before do
-        gitlab_sign_in(maintainer)
+        sign_in(maintainer)
       end
 
       it 'sees the release' do
@@ -110,7 +110,7 @@ RSpec.describe 'User views releases', :js do
 
     context('when the user is a guest') do
       before do
-        gitlab_sign_in(guest)
+        sign_in(guest)
       end
 
       it 'renders release info except for Git-related data' do