Adding strict to example aggregation causes invalid extension SQL

[willmurnane]

Adding strict to line 78 of the example aggregation made the generated SQL:

...
-- pgx-examples/aggregate/src/lib.rs:72
-- aggregate::integer_avg_state_state
CREATE FUNCTION "integer_avg_state_state"(
	"this" IntegerAvgState, /* pgx::datum::varlena::PgVarlena<aggregate::IntegerAvgState> */
	"value" integer /* core::option::Option<i32> */
) RETURNS IntegerAvgState /* pgx::datum::varlena::PgVarlena<aggregate::IntegerAvgState> */
PARALLEL SAFE IMMUTABLE STRICT STRICT
--                      ^^^ oops
LANGUAGE c /* Rust */
AS 'MODULE_PATHNAME', 'integer_avg_state_state_wrapper';

[willmurnane]

Fixed by #640.