Update RFC 0821 ready-for-release PR URL

Ember.js RFCS CI · Ember.js RFCS CI · commit 9163f0b119b7 · 2022-11-29T01:43:51.000Z
diff --git a/text/0821-public-types.md b/text/0821-public-types.md
@@ -9,6 +9,7 @@ teams:
   - learning
 prs:
   accepted: 'https://github.com/emberjs/rfcs/pull/821'
+  ready-for-release: 'https://github.com/emberjs/rfcs/pull/874'
 project-link:
 ---
 
