[Portal] Hotfix Unity sidebar link (#6688)

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## PR-Codex overview
This PR updates the sidebar navigation in the `sidebar.tsx` file, changing the name and link for a specific menu item.

### Detailed summary
- Changed the menu item name from `"Payments"` to `"Universal Bridge"`.
- Updated the `href` from `"/dotnet/pay/quickstart"` to `"/dotnet/universal-bridge/quickstart"`.

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Author: 0xFirekeeper

apps/portal/src/app/unity/v5/sidebar.tsx

@@ -108,8 +108,8 @@ export const sidebar: SideBar = {
           icon: <ExternalLinkIcon />,
         },
         {
-          name: "Payments",
-          href: "/dotnet/pay/quickstart",
+          name: "Universal Bridge",
+          href: "/dotnet/universal-bridge/quickstart",
           icon: <ExternalLinkIcon />,
         },
       ],