docs: update readme

Author: jpoehnelt

README.md

@@ -4,17 +4,10 @@ This VS Code extension provides a set of tools to help Google Workspace develope
 
 ## Features
 
-- **Preview Google Workspace Cards**: Live preview of [Card-based interfaces](https://developers.google.com/workspace/add-ons/concepts/card-interfaces) for Google Workspace Add-ons and Google Chat apps.
 - **OAuth2 Scope Linting**: Get warnings and additional information for Google Workspace [OAuth2 scopes](https://developers.google.com/identity/protocols/oauth2/scopes) in your code.
 
 ## Usage
 
-### Preview Google Workspace Cards
-
-1. Open a file containing a Google Workspace Card JSON.
-2. Select the JSON content you want to preview.
-3. Run the **Preview Google Workspace Card JSON** command from the command palette.
-
 ### OAuth2 Scope Linting
 
 Warnings and suggestions will automatically appear for OAuth2 scopes in your code.