Fix detect-tests CI job

What does this MR do and why?

The detect-tests job is failing in https://gitlab.com/gitlab-renovate-forks/gitlab/-/jobs/6326977771 because ruby:3.1-slim doesn't come with gcc and make, which is needed to build native extensions. activesupport depends on i18n, which depends on racc. racc has a native extension.

This was needed because yesterday the i81n gem added racc as a runtime dependency in 1.14.3: https://github.com/ruby-i18n/i18n/commit/2346d7c51e1ec96100a4d5a028fc6cedfd645945.

How to set up and validate locally

1. Run docker run -it ruby:3.1-slim
2. Run gem install activesupport --no-document --version 6.1.7.2

Without running apt update && apt install -y curl make gcc, this install fails.