fix(docker): Try to enable tesing old SILE images by *not* refreshing…

… them

Arch Linux does not support partial upgrades. We can't upgrade all the
base system packages and still expect a legacy version of SILE that we
didn't update to still run. We're going to be limited to testing against
versions we can install compatible packages for, possible from an
archive eventually.

Dockerfile

@@ -14,9 +14,6 @@ ARG DOCKER_HUB_CACHE=0
 
 ARG RUNTIME_DEPS
 
-# Freshen all base system packages
-RUN pacman --needed --noconfirm -Syuq && yes | pacman -Sccq
-
 # Install run-time dependencies
 RUN pacman --needed --noconfirm -Sq $RUNTIME_DEPS && yes | pacman -Sccq