Remove addition of a object type in all props

Problem/Motivation

Let's challenge this part of in https://git.drupalcode.org/project/drupal/-/blob/11.x/core/lib/Drupal/Co...

        // All props should also support "object" this allows deferring
        // rendering in Twig to the render pipeline.
        $type = $prop_schema['type'] ?? '';
        $schema['properties'][$name]['type'] = array_unique([
          ...(array) $type,
          'object',
        ]);

• The initial purpose of this addition is not clear.
• It creates a gap bewteen the schema authored by UI component owner and the schema prcossed by Drupal
• As far as I have tried (many contrib & custom SDC themes), removing it has no effect.
• It is causing annoyance in some contrib modules:
  • UI Patterns. Example: https://git.drupalcode.org/project/ui_patterns/-/blob/2.0.x/src/Plugin/U...
  • Display Builder. Example: https://git.drupalcode.org/project/display_builder/-/blob/1.0.x/src/Comp...
  • Canvas, according @wim.leers
• and (soft) blocking at least one Core issue: ✨ [PP-1] Allow schema references in Single Directory Component prop schemas Postponed

Proposed resolution

Remove this. Check if the tests are still OK.