feature #53866 [Workflow] determines places from transitions (lyrixx)

This PR was merged into the 7.1 branch.

Discussion
----------

[Workflow] determines places from transitions

| Q             | A
| ------------- | ---
| Branch?       | 7.1
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Issues        | Fix #52378
| License       | MIT

Commits
-------

ed30d81c2f [workflow] determines places form transitions

Author: fabpot

DependencyInjection/Configuration.php

@@ -484,8 +484,6 @@ private function addWorkflowSection(ArrayNodeDefinition $rootNode): void
                                                 return array_values($places);
                                             })
                                         ->end()
-                                        ->isRequired()
-                                        ->requiresAtLeastOneElement()
                                         ->prototype('array')
                                             ->children()
                                                 ->scalarNode('name')