beta regression: gltf-viewer ambiguous imports

[alexcrichton]

Discovered by crater:

$ git clone https://github.com/bwasty/gltf-viewer
$ cd gltf-viewer
$ cargo +beta build

cc @petrochenkov

[petrochenkov]

This is an expected bug-fix regression, it was previously found by the crater run in #55884 as well.
It has a dedicated test - https://github.com/rust-lang/rust/blob/master/src/test/ui/imports/issue-55884-1.rs.

[alexcrichton]

👍

cc @bwasty just to make sure you're aware!