Update collection-index.yml (#426)

Author: snapsl

_data/collection-index.yml

@@ -318,11 +318,6 @@
   contact: https://github.com/gickis/devcontainer-features/issues
   repository: https://github.com/gickis/devcontainer-features
   ociReference: ghcr.io/gickis/devcontainer-features
-- name: Flutter SDK
-  maintainer: Jarrod Colburn
-  contact: [email protected]
-  repository: https://github.com/jarrodcolburn/features
-  ociReference: ghcr.io/jarrodcolburn/features
 - name: sonikro Dev Container Features
   maintainer: Jonathan Nagayoshi
   contact: https://github.com/sonikro/devcontainer-features/issues