Fix broken link to mintlify dashboard settings in quickstart.mdx (#543)

www.dashboard.mintlify.com -> dashboard.mintlify.com

Author: prithvi2206

quickstart.mdx

@@ -174,7 +174,7 @@ your docs.
 
 Integrate your docs into your website by hosting them on a custom domain. This is included in the free plan.
 
-Navigate to your [dashboard settings](https://www.dashboard.mintlify.com/settings) to add a custom domain.
+Navigate to your [dashboard settings](https://dashboard.mintlify.com/settings) to add a custom domain.
 
 <Frame>![Custom Domain](/images/custom-domain.png)</Frame>