score.py: extract_answer() caps letters at A–E, but there are 6–7-option questions with answer F/G

### Bug

[`score.py::extract_answer()`](https://github.com/InternLM/OVO-S-Bench/blob/main/score.py#L44) hard-codes `[A-E]` in all of its regex patterns
(docstring: *"the bench uses at most 5 options"*). But the released data has questions with **up to 7 options (A–G)**. Any question whose correct answer is **F or G** can never be extracted, so it's scored wrong for every model regardless of output.

```python
from score import extract_answer
extract_answer("F") # -> '' (expected 'F')
extract_answer("Answer: F") # -> ''
```

Affected (release parquet, 1695 rows / 1722 query instances)

- Option counts: {2:454, 3:131, 4:1006, 5:1, 6:101, 7:2} → 103 rows have 6–7 options.
- 25 query instances have a correct answer of F or G, all in subcategories 1.3.1 and 2.1.2 (e.g. id=1.3.1_21, answer F = "Translating backward"; id=2.1.2_0 has both F and G). These bias the L1/L2 and Overall numbers low.

### Fix

Replace [A-E] with [A-H] (or at least [A-G]) in each pattern and update the docstring. The options are already rendered to the model as A–G, so only the scorer's extraction needs to change.