Stabilize poetry smoke fixture by ignoring transitive certifi and idna releases

[julia-thorn]

Summary

Add a certifi ignore condition to smoke-python-poetry.yaml so the Poetry smoke test remains deterministic when certifi and idna publish a new release.

Why this is needed

This came up for my dependabot-core PR - the e2e smoke tests were failing because of certifi and idna. The smoke-python-poetry fixture currently pins lockfile content that includes certifi and idna artifacts.
When a new certifi or idna release appears on PyPI, Poetry can update that transitive dependency during unrelated updates (for example requests), which causes fixture expectation drift and smoke failures.

This failure mode is:

1. External to dependabot-core behavior.
2. Time-dependent (depends on registry state at run time).
3. Unrelated to the change under test.

In other words, the smoke test becomes flaky due to upstream package churn, not due to a regression in Dependabot logic.

What changed

In smoke-python-poetry.yaml, under input.job.ignore-conditions, add:

1. dependency-name: certifi
2. source: tests/smoke-python-poetry.yaml
3. version-requirement: '>2026.2.25'
4. Repeat for idna

Effect

This keeps the fixture stable by preventing transitive certifi and idna updates beyond the fixture’s pinned baseline while preserving coverage for the intended top-level updates in this smoke scenario.

Scope

This change is intentionally narrow:

1. Only affects smoke-python-poetry.
2. Does not alter smoke workflow logic.
3. Does not change Dependabot updater behavior, only fixture policy for deterministic expectations.

Validation

1. Confirmed fixture edit is limited to a single new ignore condition in smoke-python-poetry.yaml.
2. No other smoke fixtures were modified.

[julia-thorn]

@kbukum1 tagging you because you seemed to review a similar PR recently - apologies if that's not the right ping!