Exclude yanked version on getting currentVersion

[sunng87]

Live case: https://crates.io/crates/handlebars

Handlebars' current version was 2.0.0-beta.1. Its last stable version 1.2.0 was yanked.

Previously crates.io showed 1.1.0 correctly as max version as 1.2.0 yanked. However after 2.0.0-beta.1 released, crates.io picked 1.2.0 as max one and it's said the crate is yanked.

There should be issue with max_version in krates/models.rs

Update: the data returned from backend was correct.