ci: verbose output in tracer tests (#9370)

This change provides the logging granularity necessary to debug CI
failures like [this
one](https://app.circleci.com/pipelines/github/DataDog/dd-trace-py/62261/workflows/fa599167-27fd-411b-a497-42326ec926ae/jobs/3885866)

## Checklist

- [x] Change(s) are motivated and described in the PR description
- [x] Testing strategy is described if automated tests are not included
in the PR
- [x] Risks are described (performance impact, potential for breakage,
maintainability)
- [x] Change is maintainable (easy to change, telemetry, documentation)
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed or label `changelog/no-changelog` is set
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/))
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))
- [x] If this PR changes the public interface, I've notified
`@DataDog/apm-tees`.

## Reviewer Checklist

- [x] Title is accurate
- [x] All changes are related to the pull request's stated goal
- [x] Description motivates each change
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- [x] Testing strategy adequately addresses listed risks
- [x] Change is maintainable (easy to change, telemetry, documentation)
- [x] Release note makes sense to a user of the library
- [x] Author has acknowledged and discussed the performance implications
of this PR as reported in the benchmarks PR comment
- [x] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

riotfile.py

@@ -275,7 +275,7 @@ def select_pys(min_version=MIN_PYTHON_VERSION, max_version=MAX_PYTHON_VERSION):
         ),
         Venv(
             name="tracer",
-            command="pytest {cmdargs} tests/tracer/",
+            command="pytest -v {cmdargs} tests/tracer/",
             pkgs={
                 "msgpack": latest,
                 "coverage": latest,