Issue #3607648: Fix invalid Facebook comments schema definition

Problem/Motivation

When saving the Article display configuration with a Facebook Comments field, Drupal throws a schema validation error:

The mapping definition for facebook_comments_style is invalid: its type key contains a string. It must be an array.

Proposed resolution

Updated the facebook_comments_style mapping in facebook_comments.schema.yml to use the correct nested schema definition for the type key.

Testing Reproduced the issue on Drupal 10.6.9. Confirmed the error occurs when saving the Article display configuration without changing the field settings. Applied the schema correction. Cleared Drupal cache. Confirmed the Article display configuration saves successfully without the schema validation error.