doc: release note for rpc getaddressinfo removals

doc/release-notes-19200.md

@@ -0,0 +1,7 @@
+## Wallet
+
+- Backwards compatibility has been dropped for two `getaddressinfo` RPC
+  deprecations, as notified in the 0.20 release notes. The deprecated `label`
+  field has been removed as well as the deprecated `labels` behavior of
+  returning a JSON object containing `name` and `purpose` key-value pairs. Since
+  0.20, the `labels` field returns a JSON array of label names. (#19200)