Mark correlated subqueries support as Beta

[novikd]

Changelog category (leave one):

• Improvement

Changelog entry (a user-readable short description of the changes that goes into CHANGELOG.md):

Enable correlated subqueries support by default.

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

[clickhouse-gh]

Workflow [PR], commit [ca8901f]

Summary: ❌

job_name	test_name	status	info	comment
Stateless tests (amd_msan, parallel, 2/2)		failure
	01546_log_queries_min_query_duration_ms	FAIL
Integration tests (asan, old analyzer, 1/6)		failure
	test_restore_db_replica/test.py::test_query_after_restore_db_replica[rename table-with exists table-with restart]	FAIL
Stress test (amd_tsan)		failure
	Server died	FAIL
	Hung check failed, possible deadlock found (see hung_check.log)	FAIL
	Killed by signal (in clickhouse-server.log)	FAIL
	Fatal message in clickhouse-server.log (see fatal_messages.txt)	FAIL
	Killed by signal (output files)	FAIL
	Found signal in gdb.log	FAIL