[#4646] docs(iceberg): fix Iceberg REST service doc (#4649)

### What changes were proposed in this pull request?
fix Iceberg REST service doc

### Why are the changes needed?

Fix: #4646 

### Does this PR introduce _any_ user-facing change?
no

### How was this patch tested?
just document

docs/iceberg-rest-service.md

@@ -264,7 +264,7 @@ Normally you will see the output like `{"defaults":{},"overrides":{}}%`.
 
 ### Deploying Apache Spark with Apache Iceberg support
 
-Follow the [Spark Iceberg start guide](https://iceberg.apache.org/docs/1.5.2/getting-started/) to set up Apache Spark's and Apache Iceberg's environment. 
+Follow the [Spark Iceberg start guide](https://iceberg.apache.org/docs/1.5.2/spark-getting-started/) to set up Apache Spark's and Apache Iceberg's environment.
 
 ### Starting the Apache Spark client with the Apache Iceberg REST catalog
 
@@ -312,4 +312,4 @@ Or build it manually to add custom logics:
 sh ./dev/docker/build-docker.sh --platform linux/arm64 --type iceberg-rest-server --image apache/gravitino-iceberg-rest --tag 0.6.0
 ```
 
-You could try Spark with Gravitino REST catalog service in our [playground](./how-to-use-the-playground.md#using-iceberg-rest-service).
+You could try Spark with Gravitino REST catalog service in our [playground](./how-to-use-the-playground.md#using-apache-iceberg-rest-service).