Fix error in MistralAiPropertiesTests

Author: tzolov

spring-ai-spring-boot-autoconfigure/src/test/java/org/springframework/ai/autoconfigure/mistralai/MistralAiPropertiesTests.java

@@ -44,7 +44,7 @@ public void embeddingProperties() {
 				assertThat(connectionProperties.getBaseUrl()).isEqualTo("TEST_BASE_URL");
 
 				assertThat(embeddingProperties.getApiKey()).isNull();
-				assertThat(embeddingProperties.getBaseUrl()).isNull();
+				assertThat(embeddingProperties.getBaseUrl()).isEqualTo(MistralAiCommonProperties.DEFAULT_BASE_URL);
 
 				assertThat(embeddingProperties.getOptions().getModel()).isEqualTo("MODEL_XYZ");
 			});