chore(testing): fail the build if the git tree is dirty

[emmettbutler]

This change makes CI test builds fail if they leave a dirty git tree. Combined with the fact that the nightly build recompiles requirements files, this will result in a failing nightly build when a latest dependency in the Riotfile has a new version released. The failure is accompanied by a message suggesting a requirements lockfile update.

Checklist

• Change(s) are motivated and described in the PR description.
• Testing strategy is described if automated tests are not included in the PR.
• Risk is outlined (performance impact, potential for breakage, maintainability, etc).
• Change is maintainable (easy to change, telemetry, documentation).
• Library release note guidelines are followed.
• Documentation is included (in-code, generated user docs, public corp docs).
• PR description includes explicit acknowledgement/acceptance of the performance implications of this PR as reported in the benchmarks PR comment.
• update riot dependency once feat: ensure hash consistency between lockfile and venv riot#207 is merged

Reviewer Checklist

• Title is accurate.
• No unnecessary changes are introduced.
• Description motivates each change.
• Avoids breaking API changes unless absolutely necessary.
• Testing strategy adequately addresses listed risk(s).
• Change is maintainable (easy to change, telemetry, documentation).
• Release note makes sense to a user of the library.
• Reviewer has explicitly acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment.

[pr-commenter]

Benchmarks

Comparing candidate commit fab3339 in PR branch emmett.butler/automate-nightly-lockfile-upgrades with baseline commit bfe0695 in branch 1.x.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 94 cases.