Remove outdated v3 release announcement bullet from release notes

Author: aryannikhil

docs/release-notes.rst

@@ -290,8 +290,6 @@ Bug fixes
 
 Documentation
 ~~~~~~~~~~~~~
-* Add v3.0.0 release announcement banner (:issue:`2677`).
-
 * Quickstart guide alignment with V3 API (:issue:`2697`).
 
 * Fix doctest failures related to numcodecs 0.15 (:issue:`2727`).