fix: schema name is optional for future file_format_grant

[bennylu2]

make test
CGO_ENABLED=1 go test -race -coverprofile=coverage.txt -covermode=atomic  ./...
?       github.com/Snowflake-Labs/terraform-provider-snowflake  [no test files]
ok      github.com/Snowflake-Labs/terraform-provider-snowflake/pkg/datasources  1.780s  coverage: 3.6% of statements
?       github.com/Snowflake-Labs/terraform-provider-snowflake/pkg/db   [no test files]
?       github.com/Snowflake-Labs/terraform-provider-snowflake/pkg/helpers      [no test files]
ok      github.com/Snowflake-Labs/terraform-provider-snowflake/pkg/provider     2.523s  coverage: 25.5% of statements
ok      github.com/Snowflake-Labs/terraform-provider-snowflake/pkg/resources    12.532s coverage: 46.9% of statements
ok      github.com/Snowflake-Labs/terraform-provider-snowflake/pkg/snowflake    0.426s  coverage: 46.8% of statements
?       github.com/Snowflake-Labs/terraform-provider-snowflake/pkg/testhelpers  [no test files]
ok      github.com/Snowflake-Labs/terraform-provider-snowflake/pkg/validation   0.268s  coverage: 31.8% of statements
?       github.com/Snowflake-Labs/terraform-provider-snowflake/pkg/version      [no test files]