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/20-spending_long.sql

@@ -1,5 +1,5 @@
 CREATE OR REPLACE VIEW spending_long AS
 SELECT *
 FROM long
-WHERE LEFT(item_code, 1) IN ('E', 'F', 'G', 'K')
+WHERE LEFT(item_code, 1) IN ('E', 'F', 'G')
   AND NOT is_aggregate;