Add retworkx removal release note

IvanIsCoding · IvanIsCoding · commit 2fbb343c8b25 · 2025-09-21T15:57:22.000-04:00
diff --git a/releasenotes/notes/retworkx-eol-bcbf18d805a73aed.yaml b/releasenotes/notes/retworkx-eol-bcbf18d805a73aed.yaml
@@ -0,0 +1,7 @@
+---
+deprecations:
+  - |
+    As announced in the 0.17 release, the legacy `retworkx` name has been sunset. We encourage users to depend on
+    'rustworkx' as previously instructed.
+
+    Thanks to all users that have used the library since the early days before the name change!
