Fix theilsU and contingency computation

[nihalzp]

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 bugs in the theilsU and contingency functions that caused incorrect results.

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

Details

:) SELECT theilsU(number, number) FROM numbers(5)

   ┌─theilsU(number, number)─┐
1. │                      -1 │ <- should be 1
   └─────────────────────────┘

:) SELECT contingency(number, number) FROM numbers(5)

   ┌─contingency(number, number)─┐
1. │          0.6666666666666666 │ <- should be 0.8944271909999159
   └─────────────────────────────┘

Prerequisite for #83521

[clickhouse-gh]

Workflow [PR], commit [085d07a]

Summary: ❌

job_name	test_name	status	info	comment
Integration tests (amd_tsan, 1/6)		failure
	test_storage_nats/test_nats_jet_stream.py::test_nats_overloaded_insert	FAIL	cidb, issue
BuzzHouse (amd_debug)		failure
	Logical error: 'Inconsistent AST formatting in Function_arrayElement: the query:	FAIL	cidb, issue

[nihalzp]

Integration tests (amd_tsan, 1/6)

• Flaky test_storage_nats/test_nats_jet_stream.py::test_nats_overloaded_insert #88775

BuzzHouse (amd_debug)

• Logical error: 'Inconsistent AST formatting in Function_arrayElement: the query: (STID: 1941-1bfa) #91832