Update Dockerfile template to match best practices

[rhcarvalho]

Changes:

• Remove -y flag from apt-get update, as it has no effect on that command.
• Use --no-install-recommends flag to avoid installing unnecessary dependencies.
• Use more general wildcard to remove apt package list cache.
• Remove apt-get clean command, as official Debian and Ubuntu images run it automatically.
• Update example in the documentation to match the changes.

Reference:

• https://docs.docker.com/build/building/best-practices/#apt-get