rustdoc: Fix search links to enums/typedefs

When the values in html::item_type were updated, the JS definitions were
accidentally not updated as well.

Closes #14095
auto merge of #14101 : alexcrichton/rust/issue-14095, r=kballard

When the values in html::item_type were updated, the JS definitions were
accidentally not updated as well.

Closes #14095