Either re-enable or remove devcontainer GitHub Workflow

[anaulin]

I have manually disabled the build-publish-devcontainer.yml workflow because it has been failing for several weeks now, with the error:

8 [4/5] RUN su vscode -c "cd /tmp && bundle install --gemfile /tmp/Gemfile && sudo rm /tmp/Gemfile /tmp/.ruby-version"
#8 0.437 Your Ruby version is 3.3.1, but your Gemfile specified 3.3.0
#8 ERROR: process "/bin/sh -c su vscode -c \"cd /tmp && bundle install --gemfile /tmp/Gemfile && sudo rm /tmp/Gemfile /tmp/.ruby-version\"" did not complete successfully: exit code: 18
------
 > [4/5] RUN su vscode -c "cd /tmp && bundle install --gemfile /tmp/Gemfile && sudo rm /tmp/Gemfile /tmp/.ruby-version":
0.437 Your Ruby version is 3.3.1, but your Gemfile specified 3.3.0

(example failed run: https://github.com/zinc-collective/convene/actions/runs/9178855810/job/25239670828)

It seems like the base image FROM mcr.microsoft.com/devcontainers/ruby:3.3 now contains a Ruby version that does not fit our app's current version. Looking at the tags available at https://hub.docker.com/_/microsoft-devcontainers-ruby, I don't see a way to pin the base devcontainer to have the correct version of Ruby.

Since nobody is currently using this devcontainer, I figured it is easiest to disable the workflow for now, until it can be fixed, or until we decide to remove it (since I note we have tripped on this workflow before, e.g. see #2300).

This at least will make our build green on main.