Backport PR #8127: update last_modified on rename

some storage backends may update the last_modified date on rename

alternative to  #8126

/cc @ssanderson

IPython/html/static/notebook/js/notebook.js

@@ -2084,6 +2084,7 b' define(function (require) {'
             function (json) {
                 that.notebook_name = json.name;
                 that.notebook_path = json.path;
+                that.last_modified = new Date(json.last_modified);
                 that.session.rename_notebook(json.path);
                 that.events.trigger('notebook_renamed.Notebook', json);
             }