MultiQC: switch Dockerfile from ubuntu to debian

src/docker_modules/MultiQC/1.0/Dockerfile

-FROM ubuntu:18.04
+FROM debian:stretch
 MAINTAINER Laurent Modolo
 
 ENV MULTIQC_VERSION=1.0
-ENV PACKAGES build-essential=12.4* \
-             python3-pip=9.0.1* \
-             python3-setuptools=39.0.1* \
-             python3-dev=3.6.5* \
-             python3-wheel=0.30.0* \
+ENV PACKAGES build-essential \
+             python3-pip \
+             python3-setuptools \
+             python3-dev \
+             python3-wheel \
              locales
 
 RUN apt-get update && \