refactor!: Remove unused Configuration fields

[Pijukatel]

Description

Removes the dead disable_outdated_warning, fact, and max_paid_dataset_items fields from Configuration as part of the upcoming major release cleanup (item D5 — dead config fields). The SDK defined these fields but never read them anywhere.

• src/apify/_configuration.py — the three field definitions are removed. As a consequence, Actor.get_env() no longer includes the disable_outdated_warning, fact, and max_paid_dataset_items keys, and passing these as kwargs to Configuration(...) now raises a validation error (extra='forbid').
• src/apify/_consts.py — intentionally untouched: the ActorEnvVars.MAX_PAID_DATASET_ITEMS, ApifyEnvVars.DISABLE_OUTDATED_WARNING, and ApifyEnvVars.FACT enum entries stay, since the platform still sets those environment variables. This follows the precedent of SDK_LATEST_VERSION / LOG_FORMAT, whose enum entries were kept when their config fields were removed.
• docs/02_concepts/code/11_conditional_actor_charge.py — the pay-per-result transition example now reads the ACTOR_MAX_PAID_DATASET_ITEMS environment variable directly (behavior-identical to the previous code for unset/empty values).
• docs/04_upgrading/upgrading_to_v4.md — new "Unused Configuration fields" section documenting the removal with a behavior-preserving migration snippet.
• tests/ — removed the max_paid_dataset_items parsing tests and dropped the three env vars from the randomized Actor.get_env() test.

Testing

• uv run poe check-code passes: lint, type check, and all 478 unit tests (with APIFY_TOKEN unset — one pre-existing test asserts the default token is None and fails in any environment that has the variable set).
• Verified Configuration() instantiates cleanly and a full Actor.init() / push_data() / exit() lifecycle succeeds with all three environment variables set — pydantic-settings ignores env vars without a matching field, so platform-set values are harmless.
• Verified Configuration.from_configuration() round-trips from a Crawlee Configuration and model_dump(by_alias=True) output no longer contains the removed keys.

🤖 Generated with Claude Code

https://claude.ai/code/session_01FSLrkjZjrkren6sxUw2TYR

---

Generated by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.74%. Comparing base (ed1d8eb) to head (88d6242).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1044      +/-   ##
==========================================
- Coverage   91.75%   91.74%   -0.01%     
==========================================
  Files          50       50              
  Lines        3215     3212       -3     
==========================================
- Hits         2950     2947       -3     
  Misses        265      265              

Flag	Coverage Δ
e2e	?
integration	57.34% <ø> (-0.04%)	⬇️
unit	83.06% <ø> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.