Resolve #3612718: Fix failing CKEditor/entity_embed tests on Drupal 11.4 (body field type mismatch)

The core testing profile now ships field.storage.node.body as text_long. It wins over the test module's text_with_summary storage, leaving the field config as text_with_summary against a text_long storage. This raised "Property summary is unknown" on /node/add/test_entity_embed, causing the CKEditor 5 tests to fail at waitForEditor(). Align the test body field to text_long; the summary is unused by these tests.

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