Fix bug in README example (#204)

README.md

@@ -760,7 +760,7 @@ wherever it is will be replaced by the content of
 `migrations/fixtures/functions/myfunction.sql` when the migration is committed.
 
 ```sql
---!include fixtures/functions/myfunction.sql
+--!include functions/myfunction.sql
 drop policy if exists access_by_numbers on mytable;
 create policy access_by_numbers on mytable for update using (myfunction(4, 2) < 42);
 ```