Playground UI: fix string formatting of multibyte emoji characters in the Model Output panel

[lbeurerkellner]

The playground Model Output view sometimes incorrectly renders multibyte characters like Emojis:

Query Code:

argmax
    "Provide a list of emojis that could represent a family:[FAMILY]"
from
    "chatgpt"

This is a UI-only issue and does not affect LMQL use from within Python.