Fix DbiMysqliTest::testStoreResult test for PHP 8.1

Signed-off-by: Maurício Meneghini Fauth <mauricio@fauth.dev>

test/classes/Dbal/DbiMysqliTest.php

@@ -168,11 +168,12 @@ class DbiMysqliTest extends AbstractTestCase
     public function testStoreResult(): void
     {
         $mysqli = $this->createMock(mysqli::class);
+        $mysqliResult = $this->createMock(mysqli_result::class);
         $mysqli->expects($this->once())
             ->method('store_result')
-            ->willReturn(true);
+            ->willReturn($mysqliResult);
 
-        $this->assertTrue($this->object->storeResult($mysqli));
+        $this->assertInstanceOf(mysqli_result::class, $this->object->storeResult($mysqli));
     }
 
     /**