Rollup merge of #144334 - lolbinarycat:rustdoc-span_of_fragments-revert, r=GuillaumeGomez

rustc_resolve: get rid of unused rustdoc::span_of_fragments_with_expansion

This function can cause false negatives if used incorrectly (usually "do any of the doc fragments come from a macro" is the wrong question to ask), and thus it is unused.

r? `````@GuillaumeGomez`````

Author: fmease