Remove Vertex AI Gemini model name manual setting from unit tests setup

Author: zucchivan

spring-ai-spring-boot-autoconfigure/src/test/java/org/springframework/ai/autoconfigure/vertexai/gemini/VertexAiGeminiAutoConfigurationIT.java

@@ -40,9 +40,7 @@ public class VertexAiGeminiAutoConfigurationIT {
 
 	private final ApplicationContextRunner contextRunner = new ApplicationContextRunner()
 		.withPropertyValues("spring.ai.vertex.ai.gemini.project-id=" + System.getenv("VERTEX_AI_GEMINI_PROJECT_ID"),
-				"spring.ai.vertex.ai.gemini.location=" + System.getenv("VERTEX_AI_GEMINI_LOCATION"),
-				"spring.ai.vertex.ai.gemini.chat.options.model="
-						+ VertexAiGeminiChatClient.ChatModel.GEMINI_PRO_VISION.getValue())
+				"spring.ai.vertex.ai.gemini.location=" + System.getenv("VERTEX_AI_GEMINI_LOCATION"))
 		.withConfiguration(AutoConfigurations.of(VertexAiGeminiAutoConfiguration.class));
 
 	@Test