bug #681 [Platform][VertexAI] Fix contract service id (OskarStark)

This PR was merged into the main branch.

Discussion
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[Platform][VertexAI] Fix contract service id

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| Docs?         | no
| Issues        | --
| License       | MIT

### Proof
https://github.com/symfony/ai/blob/cb6ed690875198278cca600328adb50fc67cee39/src/ai-bundle/config/services.php#L58-L59

Commits
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6671d14 [Platform][VertexAI] Fix contract service id

Author: OskarStark

src/ai-bundle/src/AiBundle.php

@@ -323,7 +323,7 @@ private function processPlatformConfig(string $type, array $platform, ContainerB
                     $platform['location'],
                     $platform['project_id'],
                     $httpClient,
-                    new Reference('ai.platform.contract.vertexai', ContainerInterface::NULL_ON_INVALID_REFERENCE),
+                    new Reference('ai.platform.contract.vertexai.gemini', ContainerInterface::NULL_ON_INVALID_REFERENCE),
                 ])
                 ->addTag('ai.platform');