Remove additional `apk update` in Dockerfile

[PeterDaveHello]

Context

I just happened to see this can be improved as I was passing by.

Description

apt upgrade with --no-cache will do the cache update thing before the upgrade, just without leaving cache. Another apt update will only spend more time and network bandwidth ;)

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.