refactor(together): Drop instructor and use native response_format …

[daavoo]

…instead.

According to https://docs.together.ai/docs/json-mode

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/any_llm/providers/together/together.py	33.33%	2 Missing ⚠️

Files with missing lines	Coverage Δ
src/any_llm/providers/together/together.py	61.53% <33.33%> (+1.24%)	⬆️

... and 29 files with indirect coverage changes

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• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[daavoo]

Can't run integration tests until https://github.com/mozilla-ai/infrastructure/issues/50