Fix typo in basic auth realm header name

changelogs/unreleased/10io-fix-www-authenticate-header-in-packages-basic-auth-helpers.yml

+---
+title: Fix the header name for basic auth authentication in package managers APIs
+merge_request: 49836
+author:
+type: fixed

lib/api/helpers/packages/basic_auth_helpers.rb

@@ -7,8 +7,8 @@ module API
         extend ::Gitlab::Utils::Override
 
         module Constants
-          AUTHENTICATE_REALM_HEADER = 'Www-Authenticate: Basic realm'
-          AUTHENTICATE_REALM_NAME = 'GitLab Packages Registry'
+          AUTHENTICATE_REALM_HEADER = 'WWW-Authenticate'
+          AUTHENTICATE_REALM_NAME = 'Basic realm="GitLab Packages Registry"'
         end
 
         include Constants

spec/support/shared_examples/requests/api/nuget_packages_shared_examples.rb

@@ -12,7 +12,7 @@ RSpec.shared_examples 'rejects nuget packages access' do |user_type, status, add
       it 'has the correct response header' do
         subject
 
-        expect(response.headers['Www-Authenticate: Basic realm']).to eq 'GitLab Packages Registry'
+        expect(response.headers['WWW-Authenticate']).to eq 'Basic realm="GitLab Packages Registry"'
       end
     end
   end