Legacy Experimental Features

WARNING

AutoBangumi 4.0 removes the old experimental_openai section. Use the LLM Parser instead.

Since 3.3, every startup migrated experimental_openai into the llm section and saved the result to the config file. 4.0 only supports upgrading from 3.3.x, so that migration has already happened. 4.0 no longer reads the old section, and drops it from the file the next time the config is saved.