Move to Ruby 3.2.0 final

[lloeki]

What does this PR do?

Move from the preview ruby image to the final one.

Motivation

So we can base ourselves on the latest thing to make things pass.

Additional Notes

CircleCI test is still disabled as tests don't pass yet, so we can change that right away as well without caring about the image being published.

How to test the change?

This should build the image in CI. As always publishing is done later.

Image can also be built locally as always, and then tested using docker compose:

docker buildx build . --platform linux/$(uname -m | sed 's/arm64/aarch64/') -f Dockerfile-3.1.1 -t ghcr.io/datadog/dd-trace-rb/ruby:3.1.1-dd
docker-compose run --rm tracer-3.2 /bin/bash

[marcotc]

Similar to https://github.com/DataDog/dd-trace-rb/pull/2497/files.

I found an issue with Appraisal not being compatible with Ruby 3.2, which is kind of a deal breaker :(

[lloeki]

Yeah @marcotc, although this PR is merely about bumping the version from 3.2.0-preview3 to 3.2.0 throughout, not about actually fixing and enabling 3.2 (which IIUC is the goal of #2497)