chore: clean up post install

Generally good practice to keep container images smaller.

Signed-off-by: Mike Fiedler <[email protected]>

Dockerfile

@@ -4,7 +4,9 @@ RUN set -x \
  && apt-get update \
  && apt-get install --no-install-recommends -y \
  build-essential git libcairo2-dev libfreetype6-dev \
- libjpeg-dev libpng-dev libz-dev
+ libjpeg-dev libpng-dev libz-dev \
+ && apt-get clean \
+ && rm -rf /var/lib/apt/lists/*
 
 RUN set -x \
  && python3 -m venv /opt/venv