PHP 8.1 fix (php-debugbar#495)

* PHP 8.1 fix

* Use supported return types

Author: RV7PR

src/DebugBar/DataCollector/AggregatedCollector.php

@@ -155,7 +155,7 @@ public function getName()
      * @param mixed $value
      * @throws DebugBarException
      */
-    public function offsetSet($key, $value)
+    public function offsetSet($key, $value): void
     {
         throw new DebugBarException("AggregatedCollector[] is read-only");
     }
@@ -164,6 +164,8 @@ public function offsetSet($key, $value)
      * @param mixed $key
      * @return mixed
      */
+    
+    #[\ReturnTypeWillChange]
     public function offsetGet($key)
     {
         return $this->collectors[$key];
@@ -173,7 +175,7 @@ public function offsetGet($key)
      * @param mixed $key
      * @return bool
      */
-    public function offsetExists($key)
+    public function offsetExists($key): bool
     {
         return isset($this->collectors[$key]);
     }
@@ -182,7 +184,7 @@ public function offsetExists($key)
      * @param mixed $key
      * @throws DebugBarException
      */
-    public function offsetUnset($key)
+    public function offsetUnset($key): void
     {
         throw new DebugBarException("AggregatedCollector[] is read-only");
     }