Remove unused properties. (#31688)

Author: lucasmichot

src/Illuminate/Support/Stringable.php

@@ -27,34 +27,6 @@ public function __construct($value = '')
         $this->value = (string) $value;
     }
 
-    /**
-     * The cache of snake-cased words.
-     *
-     * @var array
-     */
-    protected static $snakeCache = [];
-
-    /**
-     * The cache of camel-cased words.
-     *
-     * @var array
-     */
-    protected static $camelCache = [];
-
-    /**
-     * The cache of studly-cased words.
-     *
-     * @var array
-     */
-    protected static $studlyCache = [];
-
-    /**
-     * The callback that should be used to generate UUIDs.
-     *
-     * @var callable
-     */
-    protected static $uuidFactory;
-
     /**
      * Return the remainder of a string after the first occurrence of a given value.
      *