how to override nav-tabs.js?

I've created a subtheme for d8w3css. I need to make a few changes to nav-tabs.js, so I tried making acopy to my custom theme. I don't see this file in d8w3css; it seems to be inheriting it from the core seven theme. In seven.libraries.yml, I see this:

drupal.nav-tabs:
  version: VERSION
  js:
    js/nav-tabs.js: {}
  dependencies:
    - core/jquery
    - core/drupal
    - core/once
    - core/drupal.debounce
    - core/collapse

So I added this to my theme's info.yml file:

libraries-override:
  seven/drupal.nav-tabs:
    js:
      js/drupal.nav-tabs.js: js/drupal.nav-tabs.js

But it isn't picking it up (after flushing caches). What am I doing wrong or missing? Thanks, this is a great theme.