Tests: Remove WP_Term::$filter property unset() within term tests.

Removes the `unset()` of the `WP_Term::$filter` property within the term tests.

Why?

Prior to the introduction of WP_Term, the term was added to the cache when its filter property was empty. To test the cache, the tests unset this property to trigger `wp_cache_add()` in `get_term()`. [34997] changed that behavior to trigger `wp_cache_add()` when the term was not found after `wp_cache_get()` (i.e. happened in `WP_Term::get_instance()`).

Unsetting the filter property is and was not needed. Prior to `WP_Term`, the condition was an empty value. With `WP_Term`, the filter property is no longer part of the conditional logic for caching.

Follow-up to [34997], [30954], [34035].

See #61890, #61530.
Built from https://develop.svn.wordpress.org/trunk@58919


git-svn-id: http://core.svn.wordpress.org/trunk@58315 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.7-alpha-58918';
+$wp_version = '6.7-alpha-58919';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.