MacOS binary name in 0.3.0 is wrong

[paskal]

https://github.com/umputun/updater/releases/tag/v0.2.0 vs https://github.com/umputun/updater/releases/tag/v0.3.0: macos binary name is wrong, was updater_v0.2.0_macos_arm64.tar.gz, became updater_v0.3.0_darwin_arm64.tar.gz.

Reason is https://github.com/umputun/updater/pull/28, I need to fix it.