Add APIO model to ASSET benchmark ranking table

[achernodub]

• Add new state-of-the-art result for ASSET benchmark, English language.
• The result is published in the paper: [APIO: Automatic Prompt Induction and Optimization for Grammatical Error Correction and Text Simplification]
• The implementation is available at (https://arxiv.org/pdf/2508.09378) | Official |