refactor: extract duplicated sorting key lambda to improve readability

Addresses PR comment about duplicated lambda function and long line.
Extracts the sorting key logic into a reusable variable to eliminate
duplication and improve code readability while maintaining the same
order-agnostic comparison functionality.

Co-Authored-By: AJ Steers <aj@airbyte.io>

Author: devin-ai-integration[bot]

unit_tests/sources/declarative/test_concurrent_declarative_source.py

@@ -3885,12 +3885,8 @@ def test_read_concurrent_declarative_source(
         output_data = [
             message.record.data for message in _run_read(manifest, _stream_name) if message.record
         ]
-        assert sorted(
-            output_data, key=lambda x: (x.get("partition", 0), x.get("ABC", 0), x.get("AED", 0))
-        ) == sorted(
-            expected_records,
-            key=lambda x: (x.get("partition", 0), x.get("ABC", 0), x.get("AED", 0)),
-        )
+        sort_key = lambda x: (x.get("partition", 0), x.get("ABC", 0), x.get("AED", 0))
+        assert sorted(output_data, key=sort_key) == sorted(expected_records, key=sort_key)
         mock_retriever.assert_has_calls(expected_calls)