LibWeb: Make FontPlugin::generic_font_name() return FlyString

Author: https://github.com/awesomekling
Commit: 4da1f4e836
Pull-request: https://github.com/SerenityOS/serenity/pull/20969
Reviewed-by: https://github.com/shannonbooth
Reviewed-by: https://github.com/trflynn89

Userland/Libraries/LibWeb/Platform/FontPlugin.h

@@ -34,7 +34,7 @@ public:
     virtual Gfx::Font& default_font() = 0;
     virtual Gfx::Font& default_fixed_width_font() = 0;
 
-    virtual DeprecatedString generic_font_name(GenericFont) = 0;
+    virtual FlyString generic_font_name(GenericFont) = 0;
 };
 
 }