[Sparkle] Allow any reactnode description for page header (#9071)

Description
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Before, only string was allowed
Pre-requisite for dust-tt/tasks#1736

Risk
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na

Deploy
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publish sparkle

sparkle/src/components/Page.tsx

@@ -33,7 +33,7 @@ export function Page({ children, variant = "normal" }: PageProps) {
 
 interface PageHeaderProps {
   title: React.ReactNode;
-  description?: string;
+  description?: React.ReactNode;
   icon?: ComponentType<{ className?: string }>;
 }