Revert extraction setting for IndicesExtractionConfig

[cmpatino]

Revert try_extract_without_anchor to True in IndicesExtractionConfig to recover behavior in gpqa:diamond eval.

The setting was changed to try_extract_without_anchor = False to avoid false positives in GPQA. However, we ran an experiment and noticed that answers in the format \boxed{X} were being graded as incorrect even if the model gave the correct answer.

GPQA is an eval focused on evaluating the model's knowledge in science and math, so answers in the \boxed{X} format should also be valid.

Below is a summary of the effects of the change in Qwen and SmolLM3 models.

Model	Mode	try_extract_without_anchor: True	try_extract_without_anchor: False
Qwen_Qwen3-0.6B_main	/no_think	26.26	15.97
Qwen_Qwen3-1.7B_main	/no_think	31.76	24.31
Qwen_Qwen3-4B_main	/no_think	44.38	46.59
Qwen_Qwen3-0.6B_main	/think	28.16	22.54
Qwen_Qwen3-1.7B_main	/think	39.90	38.26
Qwen_Qwen3-4B_main	/think	55.30	53.66
HuggingFaceTB_SmolLM3-3B_main	/think	41.70	28.70
HuggingFaceTB_SmolLM3-3B_main	/no_think	35.70	22.35

[HuggingFaceDocBuilderDev]

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[lewtun]

LGTM but let's wait for approval from a core maintainer before merging

[clefourrier]

Can you change it in GPQA specifically? We observed we got a number of false positives in other metrics with this setting

[clefourrier]

LGTM, you can merge once tests pass

[clefourrier]

(you will have to update the tests for GPQA since you're changing the metric)