Move "Saved grants" to far right of the header links (#3919)

## Summary
Fixes #{ISSUE}

### Time to review: __5 mins__

## Changes proposed
Moves "saved grants" to end of header links:

<img width="1188" alt="image"
src="https://github.com/user-attachments/assets/551fee8a-952b-468a-b618-59010b48952e"
/>


## Testing

1. Login locally
2. See "Saved Grants" is to the far right, same as the screenshot above.

frontend/src/components/Header.tsx

@@ -63,7 +63,7 @@ const NavLinks = ({
       return anonymousNavLinks;
     }
 
-    return anonymousNavLinks.toSpliced(2, 0, {
+    return anonymousNavLinks.toSpliced(anonymousNavLinks.length, 0, {
       text: t("nav_link_saved_grants"),
       href: "/saved-grants",
     });