Update Dockerfile

[admintoth]

Current pinned img stopped working:

  #7 [2/7] RUN apt-get -qq update && apt-get -qq -y install openssh-client git >/dev/null
  #7 1.611 E: Release file for http://deb.debian.org/debian-security/dists/bullseye-security/InRelease is expired (invalid since 2d 5h 19min 8s). Updates for this repository will not be applied.
  #7 ERROR: process "/bin/sh -c apt-get -qq update && apt-get -qq -y install openssh-client git >/dev/null" did not complete successfully: exit code: 100
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   > [2/7] RUN apt-get -qq update && apt-get -qq -y install openssh-client git >/dev/null:
  1.611 E: Release file for http://deb.debian.org/debian-security/dists/bullseye-security/InRelease is expired (invalid since 2d 5h 19min 8s). Updates for this repository will not be applied.
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  Dockerfile:5
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     3 |     FROM ruby@sha256:54d09dd38d80d8b850fbff21425d9bd159f9ff7e1de1cdbcbb0b7745f5049784
     4 |     
     5 | >>> RUN apt-get -qq update && apt-get -qq -y install openssh-client git >/dev/null
     6 |     WORKDIR /app
     7 |     COPY Gemfile .
  --------------------
  ERROR: failed to build: failed to solve: process "/bin/sh -c apt-get -qq update && apt-get -qq -y install openssh-client git >/dev/null" did not complete successfully: exit code: 100
  Warning: Docker build failed with exit code 1, back off 6.902 seconds before retry.

[crohr]

@admintoth thanks, I have updated and merged #142