ci: group installation of Docker dependencies

ci: group installation of Docker dependencies

The output of CI jobs tends to be quite long-winded and hard to digest.
To help with this, many CI systems provide the ability to group output
into collapsible sections, and we're also doing this in some of our
scripts.

One notable omission is the script to install Docker dependencies.
Address it to bring more structure to the output for Docker-based jobs.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>