Document that `test.support.bytecode_helper` is new in 3.9 (GH-22618) (GH-22761)

(cherry picked from commit cf693e537dc8aaa14315a7f59baec4a31d1167d3)

Co-authored-by: Saiyang Gou <gousaiyang@163.com>

Co-authored-by: Saiyang Gou <gousaiyang@163.com>
1 file changed