fix: 如果baseurl不以/结尾，就加上

Author: hexiaochun

volcengine-java-sdk-ark-runtime/src/main/java/com/volcengine/ark/runtime/service/ArkService.java

@@ -235,6 +235,9 @@ public ArkService.Builder region(String region) {
 
         public ArkService.Builder baseUrl(String baseUrl) {
             this.baseUrl = baseUrl;
+            if (!baseUrl.endsWith("/")) {
+                this.baseUrl = baseUrl + "/";
+            }
             return this;
         }