Update log.go

[gnuhub]

go: github.com/yunify/metad/log imports
        github.com/Sirupsen/logrus: github.com/Sirupsen/logrus@v1.8.1: parsing go.mod:
        module declares its path as: github.com/sirupsen/logrus
                but was required as: github.com/Sirupsen/logrus