fix: using same logic for both hard and soft deletes

Soft delete is deleting only versions smaller than the latest version
Hard delete is deleting smaller and equal.
Making both strategies delete only smaller versions.

singer_sdk/connectors/sql.py

@@ -1212,6 +1212,6 @@ def delete_old_versions(
             conn.execute(
                 sa.text(
                     f"DELETE FROM {full_table_name} "  # noqa: S608
-                    f"WHERE {version_column_name} <= {current_version}",
+                    f"WHERE {version_column_name} < {current_version}",
                 ),
             )