[12.x] Clean up redundant type hints in docblocks (#57219)

* Update ApcStore.php

* Update ApcWrapper.php

Author: AhmedAlaa4611

src/Illuminate/Cache/ApcStore.php

@@ -36,7 +36,7 @@ public function __construct(ApcWrapper $apc, $prefix = '')
      * Retrieve an item from the cache by key.
      *
      * @param  string  $key
-     * @return mixed|null
+     * @return mixed
      */
     public function get($key)
     {

src/Illuminate/Cache/ApcWrapper.php

@@ -8,7 +8,7 @@ class ApcWrapper
      * Get an item from the cache.
      *
      * @param  string  $key
-     * @return mixed|null
+     * @return mixed
      */
     public function get($key)
     {