fsmpi-latex: Don’t install recommended packages

This avoids pulling in all the X dependencies.

fsmpi-latex/Dockerfile

 ARG DEBIAN_RELEASE=buster
 FROM registry.git.fsmpi.rwth-aachen.de/infra/ci-containers/fsmpi-base:${DEBIAN_RELEASE}
-RUN apt-get update && apt-get install -y texlive texlive-xetex latexmk lmodern fonts-cmu texlive-science texlive-publishers && rm -rf /var/lib/apt/lists/*
+RUN apt-get update && apt-get install --no-install-recommends -y texlive texlive-xetex latexmk lmodern fonts-cmu texlive-science texlive-publishers && rm -rf /var/lib/apt/lists/*