[SPARK-50320][CORE] Make --remote an official option by removing `e…

…xperimental` warning

### What changes were proposed in this pull request?

`spark-submit` has one experimental option, which is `--remote`. This PR aims to make `--remote` option be an official option by removing `experimental` warning from Apache Spark 4.0.0.

https://github.com/apache/spark/blob/0aee601dcc9875928fc526c821985d2890bdc42f/core/src/main/scala/org/apache/spark/deploy/SparkSubmitArguments.scala#L568-L572

### Why are the changes needed?

`--remote` has been used well so far and intuitively. It's unlikely for us to change it. We had better remove a warning message.

### Does this PR introduce _any_ user-facing change?

No behavior change.

### How was this patch tested?

Manual review.

**BEFORE (4.0.0-preview2)**
```
$ bin/spark-submit 2>&1 | grep xperimental | wc -l
       1
```

**AFTER**
```
$ bin/spark-submit 2>&1 | grep xperimental | wc -l
       0
```

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes apache#48850 from dongjoon-hyun/SPARK-50320.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

core/src/main/scala/org/apache/spark/deploy/SparkSubmitArguments.scala

@@ -568,8 +568,7 @@ private[deploy] class SparkSubmitArguments(args: Seq[String], env: Map[String, S
         | Spark Connect only:
         |   --remote CONNECT_URL       URL to connect to the server for Spark Connect, e.g.,
         |                              sc://host:port. --master and --deploy-mode cannot be set
-        |                              together with this option. This option is experimental, and
-        |                              might change between minor releases.
+        |                              together with this option.
         |
         | Cluster deploy mode only:
         |  --driver-cores NUM          Number of cores used by the driver, only in cluster mode