build: drop support for Go 1.16
GitLab 14.10 has been released. We can drop support for Go 1.16 according to the go version policy: https://docs.gitlab.com/ee/development/go_guide/go_upgrade.html#supporting-multiple-go-versions
Gitlab Version: v15.0.0-ee
CNG version: v15.0.0-ee (go 1.17.6)
Omnibus-builder image revision: 3.3.1 (go 1.17.6)
Gitlab Version: v14.10.0-ee
CNG version: v14.10.0-ee (go 1.17.6)
Omnibus-builder image revision: 3.2.0 (go 1.17.6)
Gitlab Version: v14.9.0-ee
CNG version: v14.9.0-ee (go 1.17.6)
Omnibus-builder image revision: 2.15.0 (go 1.17.6)
Edited by feistel