Update release note for bech32 error detection

doc/release-notes-16807.md

@@ -1,6 +1,10 @@
 Updated RPCs
 ------------
 
-- The `validateaddress` RPC now optionally returns an `error_locations` array, with the indices of
-invalid characters in the address. For example, this will return the locations of up to two Bech32
-errors.
+- The `validateaddress` RPC now returns an `error_locations` array for invalid
+addresses, with the indices of invalid character locations in the address (if
+known). For example, this will attempt to locate up to two Bech32 errors, and
+return their locations if successful. Success and correctness are only guaranteed
+if fewer than two substitution errors have been made.
+The error message returned in the `error` field now also returns more specific
+errors when decoding fails.