Update CI Config to fix randomly failing tests in Redmine 5.1.2

.github/workflows/5_1_2.yml

@@ -89,6 +89,10 @@ jobs:
       - name: Prepare Redmine source
         working-directory: redmine
         run: |
+          # Add missing :groups_users fixture to API tests
+          sed -i='' 's/^  fixtures :users/&, :groups_users/' test/integration/api_test/users_test.rb # TODO: remove next line when fixed in Redmine core
+          # Fix routes broken by Redmine core plugins tests
+          rm -f test/integration/routing/plugins_test.rb # Fix routing tests # TODO Remove this line when https://www.redmine.org/issues/38707 is fixed
           sed -i '/rubocop/d' Gemfile
           rm -f .rubocop*
           cp plugins/redmine_base_rspec/spec/support/database-${{ matrix.db }}.yml config/database.yml