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

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

@@ -4,6 +4,7 @@ package gosigar
 
 import (
 	"io/ioutil"
+	"runtime"
 	"strconv"
 	"strings"
 	"unsafe"
@@ -97,6 +98,10 @@ func (self *ProcFDUsage) Get(pid int) error {
 	return nil
 }
 
+func (self *HugeTLBPages) Get() error {
+	return ErrNotImplemented{runtime.GOOS}
+}
+
 func parseCpuStat(self *Cpu, line string) error {
 	fields := strings.Fields(line)