feat:enhanced mbpp process answer patterns

[ShikangPang]

Motivation

当我在使用mbpp测试Qwen3模型时，原有代码无法解决【BEGIN】```python这种情况下的process情况，故添加该处理patterns

Modification

调整mbpp patterns

BC-breaking (Optional)

不会

Use cases (Optional)

无

Checklist

Before PR:

• Pre-commit or other linting tools are used to fix the potential lint issues.
• Bug fixes are fully covered by unit tests, the case that causes the bug should be added in the unit tests.
• The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, like docstring or example tutorials.

After PR:

• If the modification has potential influence on downstream or other related projects, this PR should be tested with those projects.
• CLA has been signed and all committers have signed the CLA in this PR.