Docs: Clarify that `register_taxonomy()` only accepts lowercase values for the `$taxonomy` parameter.

This brings consistency with docblock used in `register_post_type()`.

Props audrasjb, bengreeley, dipakparmar443.
Fixes #56352
See #55646.

Built from https://develop.svn.wordpress.org/trunk@53873


git-svn-id: http://core.svn.wordpress.org/trunk@53432 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/taxonomy.php

@@ -390,7 +390,8 @@ function is_taxonomy_hierarchical( $taxonomy ) {
  *
  * @global WP_Taxonomy[] $wp_taxonomies Registered taxonomies.
  *
- * @param string       $taxonomy    Taxonomy key, must not exceed 32 characters.
+ * @param string       $taxonomy    Taxonomy key, must not exceed 32 characters and may only contain lowercase alphanumeric
+ *                                  characters, dashes, and underscores. See sanitize_key().
  * @param array|string $object_type Object type or array of object types with which the taxonomy should be associated.
  * @param array|string $args        {
  *     Optional. Array or query string of arguments for registering a taxonomy.

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.1-alpha-53872';
+$wp_version = '6.1-alpha-53873';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.