Track artists not shown when importing a compilation

When importing a compilation, the track artists are not shown, even if the artists will be changed by the import.

Here's an example (i was using the `--timid` flag):
```
Correcting tags from:
Ultimate 90s Sampler
To:
Ultimate 90s
URL:
https://musicbrainz.org/release/cfbdb8ac-bcc0-4f3f-9b0a-a93581ae54b1
(Similarity: 96.9%) (tracks, album) (4xCD, 2015, GB, Sony Music)
CD 1
* Everybody (Backstreet's Back) (#1) -> Everybody (Backstreet’s Back) (#1-1)
* ...Baby One More Time (#2) -> …Baby One More Time (#1-2)
* Shake Your Bon-Bon (#3) -> Shake Your Bon‐Bon (#1-3)
* It's My Life (#4) -> It’s My Life (#1-4)
* Another Night (#5) -> Another Night (#1-5)
* Genie in a Bottle (#6) -> Genie in a Bottle (#1-6)
* Gonna Make You Sweat (Everybody Dance Now) (#7) -> Gonna Make You Sweat (Everybody Dance Now) (#1-7) (artist)
* A Deeper Love (#8) -> A Deeper Love (#1-8)
* Can't Get Enough Of Your Love (#9) -> Can’t Get Enough of Your Love (#1-9)
* I'm Every Woman (#10) -> I’m Every Woman (#1-10)
* Everybody Get Up (#11) -> Everybody Get Up (#1-11)
* Waiting For Tonight (#12) -> Waiting for Tonight (#1-12)
* Blue Angels (#13) -> Blue Angels (#1-13) (artist)
[...]
[A]pply, More candidates, Skip, Use as-is, as Tracks, Group albums,
Enter search, enter Id, aBort?
```

Tracks 7 and 13 have artist field changes, but I can't see what is changed.

Reproduce the compilation import shown in the issue with the `--timid` flag and inspect the code that formats track changes. Verify the result against tracks 7 and 13 in the provided example; done means their artist field changes are visible in the import prompt.

Written by the indexing model from the issue text.