devel/grex: update to 1.4.5

[uzsolt]

Summary

Changelog: https://github.com/pemistahl/grex/releases/tag/v1.4.5

I can't figure the download link to use MASTER_SITES. Can you help?
Maintainer report: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=277582

Test Plan

Poudriere testport fine on 13.2, 13.3, 14.0 (amd64).
The make test passed.
Portlint, portfmt, portclippy are fine.

[diizzy]

There's no source tarball so USE_GITHUB is correct, in general just stick with what the handbook says about Rust and Go.