vendor: update elastic/gosigar so that it compiles on OpenBSD (#16542)

vendor/github.com/elastic/gosigar/CHANGELOG.md

vendor/github.com/elastic/gosigar/README.md

vendor/github.com/elastic/gosigar/concrete_sigar.go

vendor/github.com/elastic/gosigar/sigar_darwin.go

vendor/github.com/elastic/gosigar/sigar_freebsd.go

vendor/github.com/elastic/gosigar/sigar_interface.go

vendor/github.com/elastic/gosigar/sigar_linux.go

vendor/github.com/elastic/gosigar/sigar_linux_common.go

vendor/github.com/elastic/gosigar/sigar_openbsd.go

vendor/github.com/elastic/gosigar/sigar_stub.go

vendor/github.com/elastic/gosigar/sigar_windows.go

vendor/vendor.json