fix(anthropic): support effort="max" and remove beta headers

[ccurme (ccurme)]

effort is generally available on supported models.

[codspeed-hq]

Merging this PR will not alter performance

✅ 3 untouched benchmarks
⏩ 31 skipped benchmarks¹

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_{Comparing cc/thropic (8c7270d) with master (a5f22e7)}

Footnotes

1. 31 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩