Fix PHPStan error in AiBundleTest

Removed obsolete 'options' configuration from test. Agent configuration
doesn't support an 'options' field at the root level - model options
like temperature and max_tokens are passed at runtime via the Platform's
invoke() method, not in the configuration.

Also simplified model configuration from the old nested format with
'class' field to the simple string model identifier format.

Author: OskarStark

src/ai-bundle/tests/DependencyInjection/AiBundleTest.php

@@ -2381,13 +2381,7 @@ public function testComprehensiveMultiAgentHappyPath()
                     ],
                     // Code expert agent with memory and tools
                     'code_expert' => [
-                        'model' => [
-                            'name' => 'gpt-4',
-                            'options' => [
-                                'temperature' => 0.3,
-                                'max_tokens' => 2000,
-                            ],
-                        ],
+                        'model' => 'gpt-4',
                         'prompt' => [
                             'text' => 'You are a senior software engineer specialized in debugging and code optimization.',
                             'include_tools' => true,