fix(milvus): doSimilaritySearch to use the databaseName

 - The doSimilaritySearch method did not pass the databaseName parameter in milvus 2.3.4 and before, resulting in the use of the default database; The current milvus upgrade to 2.3.5 supports passing the databaseName parameter
    - Update doSimilaritySearch to set the database name from the Milvus configuration

Author: cycle2zhou

vector-stores/spring-ai-milvus-store/src/main/java/org/springframework/ai/vectorstore/MilvusVectorStore.java

@@ -224,6 +224,7 @@ public List<Document> doSimilaritySearch(SearchRequest request) {
 		float[] embedding = this.embeddingModel.embed(request.getQuery());
 
 		var searchParamBuilder = SearchParam.newBuilder()
+			.withDatabaseName(this.config.databaseName)
 			.withCollectionName(this.config.collectionName)
 			.withConsistencyLevel(ConsistencyLevelEnum.STRONG)
 			.withMetricType(this.config.metricType)