Rollup merge of #138318 - lolbinarycat:rustdoc-js-less-expect-error-part2, r=notriddle

Rustdoc: remove a bunch of @ts-expect-error from main.js

r? ```````@notriddle```````

Most remaining instances of ````````@ts-expect-error```````` in `search.js` and `main.js` are some sort of unchecked assertion, most of them involving nullibility, and we have yet to decide on how to handle these.

Author: Manishearth