Problem/Motivation
#3028501: Enable header-based proactive content negotiation with optimizations and opt-outs available. introduced the an enable_content_negotiation setting to default.settings.php as a BC-layer. It is used in ContentNegotiationCompilerPass.php to override a services.yml parameter.
Proposed resolution
Remove the setting from `default.settings.php` and remove the code that respects it from ContentNegotiationCompilerPass.php.
Remaining tasks
User interface changes
None.