refactor(sql): Simplify primary key fallback logic with one-liner

Address @aaronsteers feedback to use more concise approach:
pks = configured_stream.primary_key or configured_stream.stream.source_defined_primary_key or []

This maintains exact same functionality while being more readable.

Co-Authored-By: AJ Steers <[email protected]>

Author: devin-ai-integration[bot]

airbyte_cdk/sql/shared/catalog_providers.py

@@ -122,12 +122,11 @@ def get_primary_keys(
     ) -> list[str]:
         """Return the primary keys for the given stream."""
         configured_stream = self.get_configured_stream_info(stream_name)
-        pks = configured_stream.primary_key
-
-        if not pks:
-            pks = configured_stream.stream.source_defined_primary_key
-            if not pks:
-                return []
+        pks = (
+            configured_stream.primary_key
+            or configured_stream.stream.source_defined_primary_key
+            or []
+        )
 
         normalized_pks: list[list[str]] = [
             [LowerCaseNormalizer.normalize(c) for c in pk] for pk in pks