analytics: update SAT creation instructions (#1264)

<!-- Explain the changes introduced in your PR -->
Received feedback that the current SAT generation instructions were
confusing
https://sourcegraph.slack.com/archives/C05GJPTSZCZ/p1752681671517589


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Co-authored-by: James Cotter <[email protected]>

Author: kalanchan

docs/analytics/api.mdx

@@ -6,9 +6,9 @@ The Sourcegraph Analytics API is an API that provides programmatic access to you
 
 For Sourcegraph Analytics, you can generate an access token for programmatic access. Tokens are long-lived with an optional expiry and have the same permissions to access instance data as the user who created them.
 
-### Token management APIs
+### Getting Started
 
-Token management is currently only available via the Sourcegraph Analytics API. Token management APIs are authenticated via the `cas` session cookie.
+Access tokens are created using the `cas` cookie for authentication to the token creation endpoint. Access tokens are longer lived than the `cas` cookie making them more suitable for programmatic access to the Sourcegraph Analytics API.
 
 - Sign in to [Sourcegraph Analytics](https://analytics.sourcegraph.com).
 - Retrieve your session cookie, `cas`, from your browser's developer tools.