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`.

src/wallet/rpcwallet.cpp

@@ -3843,12 +3843,11 @@ UniValue getaddressinfo(const JSONRPCRequest& request)
     // associated with an address, but we return an array so the API remains
     // stable if we allow multiple labels to be associated with an address in
     // the future.
-    //
-    // DEPRECATED: The previous behavior of returning an array containing a JSON
-    // object of `name` and `purpose` key/value pairs has been deprecated.
     UniValue labels(UniValue::VARR);
     std::map<CTxDestination, CAddressBookData>::iterator mi = pwallet->mapAddressBook.find(dest);
     if (mi != pwallet->mapAddressBook.end()) {
+        // DEPRECATED: The previous behavior of returning an array containing a
+        // JSON object of `name` and `purpose` key/value pairs is deprecated.
         if (pwallet->chain().rpcEnableDeprecated("labelspurpose")) {
             labels.push_back(AddressBookDataToJSON(mi->second, true));
         } else {

test/functional/rpc_getaddressinfo_labels_purpose_deprecation.py

@@ -4,8 +4,8 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """
 Test deprecation of RPC getaddressinfo `labels` returning an array
-containing a JSON hash of `name` and purpose` key-value pairs. It now
-returns an array of label names.
+containing a JSON object of `name` and purpose` key-value pairs. It now
+returns an array containing only the label name.
 
 """
 from test_framework.test_framework import BitcoinTestFramework