Update Pub/Sub getting started landing page, remove duplicate Flutter tile, redirect SDK set up to this page

Author: GregHolmes

src/pages/docs/getting-started/index.mdx

@@ -6,6 +6,7 @@ redirect_from:
   - /docs/quick-start-guide
   - /docs/root/quick-start-guide
   - /docs/getting-started/quickstart
+  - /docs/getting-started/setup
 ---
 
 Get started with Ably Pub/Sub by choosing your language or framework.
@@ -46,12 +47,6 @@ These are your first steps towards building a realtime application that can effo
     image: 'icon-tech-swift',
     link: '/docs/getting-started/swift',
   },
-  {
-    title: 'Flutter',
-    description: 'Start building with Pub/Sub using Ably\'s Flutter SDK.',
-    image: 'icon-tech-flutter',
-    link: '/docs/getting-started/flutter',
-  },
   {
     title: 'Objective-C',
     description: 'Start building with Pub/Sub using Ably\'s Objective-C SDK.',