fix(discord): remove default selection from model picker provider dropdown

Discord doesn't fire the select callback when clicking an already-selected
default option (no change detected). This prevented users from selecting
the current provider to browse its models. The 'current' indicator is
already shown via the description field.

gateway/platforms/discord.py

@@ -2637,7 +2637,6 @@ if DISCORD_AVAILABLE:
                     discord.SelectOption(
                         label=label[:100],
                         value=p["slug"],
-                        default=bool(p.get("is_current")),
                         description=desc,
                     )
                 )