build: fix a compile error with Go 1.21

[knqyf263]

Description

go get go@1.20 downgrades the required Go version and the dependency versions (github.com/sigstore/rekor this time). See the comment for details.

Related issues

• Close build: fix a compile error with Go 1.21 #5338

Related PRs

• chore(deps): bump github.com/sigstore/rekor from 1.2.1 to 1.3.0 #5304

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).

[aminvakil]

I've opened aminvakil/aur#308 to test on go 1.21 and my environment after patching this PR.

[aminvakil]

And I just saw that is going to be merged :) I'll report here anyway, thanks!

[aminvakil]

It built correctly using this PR.
https://github.com/aminvakil/aur/actions/runs/6417778330/job/17424225249?pr=308

Thanks!