chore: add issue link to EXCLUDE WHERE clause fixture

Author: pyramation

__fixtures__/kitchen-sink/misc/issues.sql

@@ -76,6 +76,7 @@ select "AA" from "table_name";
 -- https://github.com/constructive-io/pgsql-parser/issues/217
 SELECT CAST(t.date AT TIME ZONE $$America/New_York$$ AS text)::date FROM tbl t;
 
+-- https://github.com/constructive-io/pgsql-parser/issues/287
 -- EXCLUDE constraint with WHERE clause (partial exclusion constraint)
 -- The deparser drops the WHERE clause from EXCLUDE USING ... WHERE (...)
 CREATE TABLE test_exclude_where (