Package dev-util/shfmt is outdated

[v3.4.2](https://github.com/mvdan/sh/releases/tag/v3.4.2) is available upstream while version in the repo is [v3.1.2](https://github.com/Dr-Terrible/go-overlay/blob/master/dev-util/shfmt/shfmt-3.1.2.ebuild) (As of 12:00 PM GMT+6, 30/01/2022).