rules_go should work with Go versions older than 1.20

[shs96c]

What version of gazelle are you using?

0.37.0

What version of rules_go are you using?

0.48.0

What version of Bazel are you using?

7.2.0

Does this issue reproduce with the latest releases of all the above?

Yes

What operating system and processor architecture are you using?

macOS

What did you do?

Attempted to use an older version of Go (1.18) to build a project

What did you expect to see?

Everything should Just Work

What did you see instead?

go_mod_download.go uses errors.Join which was introduced in Go 1.20. Because of this, it could not be compiled, which causes runs of gazelle to fail.