tutorials: web blog fixes

tutorials/code/blog/article.v

@@ -7,9 +7,9 @@ struct Article {
 }
 
 pub fn (app &App) find_all_articles() []Article {
-	db := app.db
-	articles := db.select from Article
-	return articles
+	return sql app.db {
+		select from Article
+	}
 }