Tests: Use `assertSame()` in some `WP_Theme_JSON` tests.

This ensures that not only the return values match the expected results, but also that their type is the same.

Previously committed in [54402], these instances appear to be accidentally reverted to `assertEquals()` in [54443].

Follow-up to [52275], [54162], [54402], [54443].

See #55654.
Built from https://develop.svn.wordpress.org/trunk@54446


git-svn-id: http://core.svn.wordpress.org/trunk@54005 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.1-beta3-54445';
+$wp_version = '6.1-beta3-54446';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.