[SPARK-50320][CORE] Make --remote an official option by removing experimental warning

[dongjoon-hyun]

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.

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

Lines 568 to 572 in 0aee601

	| 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.

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.

[dongjoon-hyun]

cc @HyukjinKwon