Update Dockerfile.admin-tools-tls

[nbarrow-inspire-labs]

Solving permission error while running update-ca-certificates (see https://community.temporal.io/t/docker-compose-tls-installation-failed/7895)

What was changed

A single line was added to solve the following error while running bash ./tls/run-tls.sh following the tls setup README.md:

 => ERROR [temporal-admin-tools 3/3] RUN update-ca-certificates                                                                                                                                                  0.2s
------
 > [temporal-admin-tools 3/3] RUN update-ca-certificates:
#0 0.203 Failed to open temporary file /etc/ssl/certs/bundleXXXXXX for ca bundle
------
failed to solve: process "/bin/bash -c update-ca-certificates" did not complete successfully: exit code: 1

Why?

By adding the line USER root, docker is able to successfully execute the update-ca-certificates command located in the changed file.

Checklist

2. How was this tested: Built and executed on Ubuntu 22.04 according to the README.md.

3. Any docs updates needed? Not to my knowledge.

[ghost]

Review on Crocodile

[CLAassistant]

All committers have signed the CLA.

[cdimitroulas]

Any chance we could get this merged? This error prevents running the ./tls/run-tls.sh script for all users at the moment :)