Drop ununsed import in windows specific code

[dims]

in d3fc3b5 the usage of user.Current() was dropped, but the corresponding import was left "os/user"

found in kubernetes CI jobs:

• https://prow.k8s.io/view/gs/kubernetes-ci-logs/logs/ci-kubernetes-unit-dependencies/2002303465103036416
• https://prow.k8s.io/view/gs/kubernetes-ci-logs/logs/ci-kubernetes-e2e-kind-dependencies/2002337439577804800

confirmed fix by running https://github.com/dims/typecheck

❯ typecheck
type-checking windows/arm64
type-checking darwin/arm64
ERROR(windows/arm64): /Users/dsrinivas/go/src/github.com/godbus/dbus/auth_sha1_windows.go:10:2: "os/user" imported and not used
type-checking windows/386
type-checking linux/amd64
ERROR(windows/386): /Users/dsrinivas/go/src/github.com/godbus/dbus/auth_sha1_windows.go:10:2: "os/user" imported and not used
type-checking windows/amd64
ERROR(windows/amd64): /Users/dsrinivas/go/src/github.com/godbus/dbus/auth_sha1_windows.go:10:2: "os/user" imported and not used
type-checking linux/arm
type-checking linux/386
type-checking linux/ppc64le
type-checking linux/arm64
type-checking linux/s390x
type-checking darwin/amd64

cc @kolyshkin

[dims]

xref: kubernetes/kubernetes#135864

[kolyshkin]

My bad; the fix LGTM

[kolyshkin]

@guelfey PTAL; this is a followup fix to #422 which introduces a Windows only regression in v5.2.1 (missed as we don't have a CI job to compile code on Windows).