fix: drop the inert K prefix from the spending flow prefixes

K matches zero rows corpus-wide (audited pipeline-side). Numerically inert;
removed so the code stops implying a prefix the data never had.

inst/sql/22-spending_long_harmonized.sql

@@ -3,4 +3,4 @@ SELECT * REPLACE (harmonized_code AS item_code)
 FROM long
 WHERE NOT is_aggregate
   AND harmonized_code IS NOT NULL
-  AND LEFT(harmonized_code, 1) IN ('E', 'F', 'G', 'K');
+  AND LEFT(harmonized_code, 1) IN ('E', 'F', 'G');