[MINOR][CORE] Add @Deprecated for `SparkLauncher#DEPRECATED_CHILD_C…

…ONNECTION_TIMEOUT`

### What changes were proposed in this pull request?
This pr just add `Deprecated` for `SparkLauncher#DEPRECATED_CHILD_CONNECTION_TIMEOUT`.

### Why are the changes needed?
From the javadoc, `DEPRECATED_CHILD_CONNECTION_TIMEOUT` has been deprecated, so it should carry a `Deprecated` marker.

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

### How was this patch tested?
Pass GitHub Actions

### Was this patch authored or co-authored using generative AI tooling?
No

Closes #43374 from LuciferYang/DEPRECATED_CHILD_CONNECTION_TIMEOUT-Deprecated.

Authored-by: yangjie01 <yangjie01@baidu.com>
Signed-off-by: yangjie01 <yangjie01@baidu.com>

launcher/src/main/java/org/apache/spark/launcher/SparkLauncher.java

@@ -99,6 +99,7 @@ public class SparkLauncher extends AbstractLauncher<SparkLauncher> {
    * @deprecated use `CHILD_CONNECTION_TIMEOUT`
    * @since 1.6.0
    */
+  @Deprecated
   public static final String DEPRECATED_CHILD_CONNECTION_TIMEOUT =
     "spark.launcher.childConectionTimeout";