[3.13] Docs: Add cross-reference for `positional_item` in the `calls` productionlist (GH-129977) (GH-135941)

Docs: Add cross-reference for `positional_item` in the `calls` productionlist (GH-129977)

Add missing hyperlink for `positional_item`
(cherry picked from commit d2154912b3b10823c138e904e74f2a1e7e7ca96c)

Co-authored-by: HarryLHW <123lhw321@gmail.com>