doc: address pr17578 review feedback

- https://github.com/bitcoin/bitcoin/pull/17578#discussion_r363975411
- https://github.com/bitcoin/bitcoin/pull/17578#discussion_r363969721
- https://github.com/bitcoin/bitcoin/pull/17578#discussion_r362703553

doc/release-notes-17578.md

@@ -4,5 +4,5 @@ Deprecated or removed RPCs
 - The `getaddressinfo` RPC `labels` field now returns an array of label name
   strings. Previously, it returned an array of JSON objects containing `name` and
   `purpose` key/value pairs, which is now deprecated and will be removed in
-  0.21. To re-enable the previous behavior, launch bitcoind with
+  0.21. To re-enable the previous behavior, launch with
   `-deprecatedrpc=labelspurpose`.