dash workaround not needed anymore

Dockerfile

@@ -1,10 +1,7 @@
 FROM debian:unstable as builder
-# "apt-mark hold dash" is a temporary workaround due to dash/0.5.12-2
-# to dash/0.5.12-4 update which results in a dpkg failure (in dist-upgrade)
 # hadolint ignore=DL3005,DL3008,DL3015,DL3009,SC2046
 RUN sed -i 's/main/main non-free non-free-firmware contrib/' /etc/apt/sources.list.d/debian.sources && \
     apt-get update && \
-    apt-mark hold dash && \
     apt-get dist-upgrade -y && \
     apt-get install ca-certificates git gcc make libssl-dev zlib1g-dev yasm \
                     $([ "$(dpkg --print-architecture)" = "armel" ] && echo pocl-opencl-icd pocl-opencl-icd ocl-icd-opencl-dev) \
@@ -39,7 +36,6 @@ LABEL org.opencontainers.image.authors="[email protected]"
 # hadolint ignore=DL3005,DL3008,SC2046
 RUN sed -i 's/main/main non-free non-free-firmware contrib/' /etc/apt/sources.list.d/debian.sources && \
     apt-get update && \
-    apt-mark hold dash && \
     apt-get dist-upgrade -y && \
         apt-get install zlib1g libc6 libgmp10 libpcap0.8 libbz2-1.0 \
                         $([ "$(dpkg --print-architecture)" = "armel" ] && echo pocl-opencl-icd) \