Add warning to outdated SendGrid release note (#9830)

* Remove outdated SendGrid platform addition release note

This release note announced the 2024 transition to SendGrid API for transactional emails, which is now completed and no longer relevant.

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

* Remove unused SendGrid release note image

Removes wp-forgot-password-form.png that was only used in the now-deleted SendGrid release note.

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

* Remove accidentally committed settings file

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

* Revert commits that deleted release note entry

* Add warning alert w/editorial note

---------

Co-authored-by: Claude Sonnet 4.5 <[email protected]>
Co-authored-by: Rachel Whitton <[email protected]>

Author: 3 people

src/source/releasenotes/2024-05-10-sendgrid-transactional-emails.md

@@ -3,6 +3,15 @@ title: "Transactional emails now sent via SendGrid API"
 published_date: "2024-05-10"
 categories: [new-feature, wordpress, drupal]
 ---
+
+<Alert type="warning" title="Warning">
+
+**Editorial note:** This entry describes a feature that is not available on Pantheon today. We continue to recommend integrating a third-party service provider instead. For details, see [related documentation](/email).
+
+_January 21, 2026_
+
+</Alert>
+
 Beginning this week, Pantheon will start transitioning individual WordPress and Drupal sites to use Sendgrid's API for the delivery of outgoing email initiated by these CMSes. We expect all sites to be fully transitioned by May 31, 2024. This change is happening at the platform level, not within the CMS code or configuration, and therefore requires no action by customers. 
 
 ## Reason for transition