time: add missing "os" import to zoneinfo_test.go
time: add missing "os" import to zoneinfo_test.go

Updates #45448

Change-Id: I2e79ae6b9cf43a481aa703578712619ea344e421
Reviewed-on: https://go-review.googlesource.com/c/go/+/310212
Trust: Damien Neil <7e091e9a80da888fcd7836fd3c6b7b85f4677c12@google.com>
Run-TryBot: Damien Neil <7e091e9a80da888fcd7836fd3c6b7b85f4677c12@google.com>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

CAFxX/go,cloudflare/go,golang/go,CAFxX/go,nawawi/go,cloudflare/go,nawawi/go,nawawi/go,CAFxX/go,cloudflare/go,cloudflare/go,golang/go,cloudflare/go,CAFxX/go,nawawi/go,golang/go,CAFxX/go,CAFxX/go,cloudflare/go,CAFxX/go,golang/go,golang/go,cloudflare/go,cloudflare/go,CAFxX/go,golang/go,nawawi/go,nawawi/go,nawawi/go,golang/go,nawawi/go,golang/go