devel/electron38: update to 38.2.1

While here, fix build with rust 1.90.[1]

Changelog: https://github.com/electron/electron/releases/tag/v38.2.1

Reported by: GitHub (watch releases)
Obtained from: https://cgit.freebsd.org/ports/commit/?id=a448aeb00153c3465a30ff41ecf43f8896a50d52 [1]