Limit file types in assistant edit form

[SmittieC]

Supported file types for code interpreter: https://platform.openai.com/docs/assistants/tools/code-interpreter/supported-files
Supported file types for file search: https://platform.openai.com/docs/assistants/tools/file-search/supported-files

We're limiting the file types when uploading files through the chat UI, but not when uploading it in the assistant's edit form. We need to do it there as well.