[UI] Improve the design of LLM opt-in button

[SaharMehrpour]

• The current design is bulky and wasting space.
• activeLLM is an internal terminology.
• Not clear what should be the API key. Maybe add an info button to explain it.
• There is no cancel button.
• The error message is displayed in a grey text.

[SaharMehrpour]

The functionality is removed.