Coding Standards: Remove the custom property for the FileName sniff.

Test files should comply with the naming conventions accepted by PHPUnit, not with the WP naming conventions.

While the `WordPress.File.FileName` sniff makes a best effort to prevent throwing errors for files containing test classes, the recommended manner to deal with test files is to exclude the complete test directory from being subject to this sniff.

This updates the ruleset to follow the recommendation.

Follow-up to [42346], [45607].

Props jrf.
See #59161.
Built from https://develop.svn.wordpress.org/trunk@56594


git-svn-id: http://core.svn.wordpress.org/trunk@56106 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.4-alpha-56593';
+$wp_version = '6.4-alpha-56594';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.