Font Library: Improve 'No fonts installed' state when fonts are installed but not activated

[akasunil]

What?

Fixes https://github.com/WordPress/gutenberg/issues/63418

Why?

Styles panel shows a 'No fonts installed.` text event when fonts are installed, but not activated.

How?

Added condition to display message conditionally. Now it will display 'No fonts activated.` when fonts are installed but not activated.

Testing Instructions

• Open Styles panel , go to typography
• If you don't have any font installed, it should show 'No fonts installed.`
• If you have any font installed, it should show 'No fonts activated.`