fix: do not grant "node" user sudo access when using run_in_container.sh (#627)

This exploration came out of my review of
https://github.com/openai/codex/pull/414.

`run_in_container.sh` runs Codex in a Docker container like so:


bd1c3deed9/codex-cli/scripts/run_in_container.sh (L51-L58)

But then runs `init_firewall.sh` to set up the firewall to restrict
network access.

Previously, we did this by adding `/usr/local/bin/init_firewall.sh` to
the container and adding a special rule in `/etc/sudoers.d` so the
unprivileged user (`node`) could run the privileged `init_firewall.sh`
script to open up the firewall for `api.openai.com`:


31d0d7a305/codex-cli/Dockerfile (L51-L56)

Though I believe this is unnecessary, as we can use `docker exec --user
root` from _outside_ the container to run
`/usr/local/bin/init_firewall.sh` as `root` without adding a special
case in `/etc/sudoers.d`.

This appears to work as expected, as I tested it by doing the following:

```
./codex-cli/scripts/build_container.sh
./codex-cli/scripts/run_in_container.sh 'what is the output of `curl https://www.openai.com`'
```

This was a bit funny because in some of my runs, Codex wasn't convinced
it had network access, so I had to convince it to try the `curl`
request:


![image](https://github.com/user-attachments/assets/80bd487c-74e2-4cd3-aa0f-26a6edd8d3f7)

As you can see, when it ran `curl -s https\://www.openai.com`, it a
connection failure, so the network policy appears to be working as
intended.

Note this PR also removes `sudo` from the `apt-get install` list in the
`Dockerfile`.

codex-cli/Dockerfile

@@ -20,7 +20,6 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
   less \
   man-db \
   procps \
-  sudo \
   unzip \
   ripgrep \
   zsh \
@@ -47,10 +46,10 @@ RUN npm install -g codex.tgz \
   && rm -rf /usr/local/share/npm-global/lib/node_modules/codex-cli/tests \
   && rm -rf /usr/local/share/npm-global/lib/node_modules/codex-cli/docs
 
-# Copy and set up firewall script
-COPY scripts/init_firewall.sh /usr/local/bin/
+# Copy and set up firewall script as root.
 USER root
-RUN chmod +x /usr/local/bin/init_firewall.sh && \
-  echo "node ALL=(root) NOPASSWD: /usr/local/bin/init_firewall.sh" > /etc/sudoers.d/node-firewall && \
-  chmod 0440 /etc/sudoers.d/node-firewall
+COPY scripts/init_firewall.sh /usr/local/bin/
+RUN chmod 500 /usr/local/bin/init_firewall.sh
+
+# Drop back to non-root.
 USER node