Simplify RemoveCheckToStringNodeVisitor when Twig 4.0 is released

Problem/Motivation

🐛 Performance Degraded after update to twig 3.14.2 Active is replacing Twig's \Twig\Node\CheckToStringNode with a Drupal optimised version. When we update to Twig 4.0 we can remove code in \Drupal\Core\Template\RemoveCheckToStringNodeVisitor as the spread attribute has been removed there.

Proposed resolution

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet