Fix approx_top_k() to respect threshold parameter when called with si…

[raimannma]

Changelog category (leave one):

• Bug Fix (user-visible misbehavior in an official stable release)

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

Fix top_k to respect the threshold parameter when called with a single argument. Closes #88757

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

Explaination

SELECT approx_top_k(50)(number) FROM numbers(200);

Previously this returned 30 rows now it returns 50 rows

Closes #88757

[raimannma]

@UnamedRus Can you take a look at this PR? I think it's the exact change you described here.

[clickhouse-gh]

Workflow [PR], commit [a70ebf9]

Summary: ❌

job_name	test_name	status	info	comment
Stateless tests (amd_asan, distributed plan, parallel, 2/2)		failure
	03047_on_fly_mutations_non_deterministic_replace	FAIL	cidb
Stateless tests (amd_ubsan, parallel)		failure
	00900_long_parquet_load	FAIL	cidb, flaky
Integration tests (amd_asan, old analyzer, 4/6)		failure
	test_scheduler_cpu_preemptive/test.py::test_downscaling[cpu-slot-preemption-timeout-1ms]	FAIL	cidb
	OOM in dmesg	FAIL	cidb

[yariks5s]

00900_long_parquet_load - #88893

Integration tests (amd_asan, old analyzer, 4/6) - flaky

03047_on_fly_mutations_non_deterministic_replace - flaky