Add -k to keyserver curl command

This command seems to inexplicably fail in Docker builds, despite
working on the CLI, similar to what happened with the command directly
above it in c257d6071c. Fix it in the same
way by adding `-k`.

Dockerfile.arm

@@ -38,7 +38,7 @@ COPY --from=qemu /usr/bin/qemu-arm-static /usr/bin
 RUN apt-get update \
  && apt-get install --no-install-recommends --no-install-suggests -y ca-certificates gnupg curl && \
  curl -ks https://repo.jellyfin.org/debian/jellyfin_team.gpg.key | apt-key add - && \
- curl -s https://keyserver.ubuntu.com/pks/lookup?op=get\&search=0x6587ffd6536b8826e88a62547876ae518cbcf2f2 | apt-key add - && \
+ curl -ks https://keyserver.ubuntu.com/pks/lookup?op=get\&search=0x6587ffd6536b8826e88a62547876ae518cbcf2f2 | apt-key add - && \
  echo 'deb [arch=armhf] https://repo.jellyfin.org/debian buster main' > /etc/apt/sources.list.d/jellyfin.list && \
  echo "deb http://ppa.launchpad.net/ubuntu-raspi2/ppa/ubuntu bionic main">> /etc/apt/sources.list.d/raspbins.list && \
  apt-get update && \