[CI] Rust job always runs on AppVeyor

[asfimport]

... even if no Rust-affecting files are modified. Looks like the job name was changed but the detection script wasn't updated.

See e.g. https://ci.appveyor.com/project/ApacheSoftwareFoundation/arrow/build/1.0.8087/job/oxnuhwld3yb7mvsv

Reporter: Antoine Pitrou / @pitrou
Assignee: Antoine Pitrou / @pitrou

PRs and other links:

• GitHub Pull Request #2620

_{Note: This issue was originally created as ARROW-3322. Please see the migration documentation for further details.}

[asfimport]

Krisztian Szucs / @kszucs:
Issue resolved by pull request 2620
#2620