Dashboard: Fix table row not clickable in safari because of sticky thead (#6783)

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## PR-Codex overview
This PR focuses on updating the `className` property of the `<thead>` component in two files to simplify its styling.

### Detailed summary
- Updated `className` in `<thead>` component in `apps/dashboard/src/@/components/ui/table.tsx`:
  - Changed from a complex string with multiple classes to a simpler string: `"relative border-b bg-background"`.
- Applied the same change in `apps/playground-web/src/components/ui/table.tsx`.

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Author: MananTank

apps/dashboard/src/@/components/ui/table.tsx

@@ -24,11 +24,7 @@ const TableHeader = React.forwardRef<
 >(({ className, ...props }, ref) => (
   <thead
     ref={ref}
-    className={cn(
-      "border-border border-b bg-background",
-      "sticky top-0 z-20 border-none before:absolute before:inset-0 before:border-border before:border-b",
-      className,
-    )}
+    className={cn("relative border-b bg-background", className)}
     {...props}
   />
 ));

apps/playground-web/src/components/ui/table.tsx

@@ -24,11 +24,7 @@ const TableHeader = React.forwardRef<
 >(({ className, ...props }, ref) => (
   <thead
     ref={ref}
-    className={cn(
-      "border-border border-b bg-background",
-      "sticky top-0 z-20 border-none before:absolute before:inset-0 before:border-border before:border-b",
-      className,
-    )}
+    className={cn("relative border-b bg-background", className)}
     {...props}
   />
 ));