fix: add explicit type cast to resolve operator ambiguity in i3

Add explicit `::int2[]` cast to `key_cols` parameter in the i3 foreign
key check query. This resolves "operator is not unique" errors that can
occur in certain PostgreSQL environments (such as Google CloudSQL).

The error occurs when PostgreSQL cannot determine which @> operator to
use between smallint[] operands. By explicitly casting both sides to
int2[], we eliminate any ambiguity.

While standard PostgreSQL installations (including those with intarray
extension) may not exhibit this error, the explicit cast is a best
practice that ensures consistent behavior across all environments.

Fixes #62

Author: NikolayS

sql/i3_non_indexed_fks.sql

@@ -63,7 +63,7 @@ with fk_actions ( code, action ) as (
   join fk_cols_list using (fkoid)
   left join index_list on
     conrelid = indrelid
-    and (indkey::int2[])[0:(array_length(key_cols,1) -1)] operator(pg_catalog.@>) key_cols
+    and (indkey::int2[])[0:(array_length(key_cols,1) -1)] operator(pg_catalog.@>) key_cols::int2[]
 
 ), fk_perfect_match as (
   select fkoid