Update id/ids notice in changelog

CHANGELOG.md

@@ -17,6 +17,11 @@ Canonical reference for changes, improvements, and bugfixes for Boundary.
   target's session authorization call.
 * The `grant_scope_id` field on roles is now deprecated in favor of the multiple
   grant scope support.
+* The deprecation notice for the `id` field in grant changing to `ids` in 0.13.1
+  specified that it would be removed in 0.15.0. Instead, this will be removed in
+  0.16.0. Existing grants already submitted into the system will still work, but
+  the API will no longer accept adding or setting grants containing the `id`
+  field in 0.16.0.
 
 ### New and Improved