Update blog with release notes URL

Author: dondonz

blog/2023-07-11-v21-released.md

@@ -8,9 +8,4 @@ We are pleased to announce the release of graphql-java v21.0! Thanks to everyone
 
 And a very Happy 8th Birthday to graphql-java, who celebrated their birthday last week!
 
-## Breaking change release: new Java 11 minimum
-This is a breaking change release. This is the first release of graphql-java to use Java 11.
-
-TODO: add other release highlights
-
-See the full release notes on [GitHub](TODO: add link)
+This is a **breaking change** release, including upgrading to Java 11 and changes to `parseValue` coercion. See the full release notes on [GitHub](https://github.com/graphql-java/graphql-java/releases/tag/v21.0).