Match upstream syntax

LibreNMS/ObjectCache.php

@@ -91,7 +91,7 @@ class ObjectCache implements ArrayAccess
      * @return mixed
      */
     #[\ReturnTypeWillChange]
-    public function offsetGet($obj)
+    public function offsetGet($obj): mixed
     {
         if (isset($this->data[$obj])) {
             if (isset($this->data[$obj]['value'])) {

LibreNMS/Util/DynamicConfigItem.php

@@ -225,7 +225,7 @@ class DynamicConfigItem implements \ArrayAccess
     }
 
     #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    public function offsetGet($offset): mixed
     {
         return isset($this->$offset) ? $this->$offset : null;
     }