Issue #3274938: Remove deprecated public Backbone and Underscore libraries

core/scripts/js/vendor-update.js

@@ -79,10 +79,6 @@ const assetsFolder = `${coreFolder}/assets/vendor`;
       library: 'internal.backbone',
       files: ['backbone.js', 'backbone-min.js', 'backbone-min.map'],
     },
-    // Only used to update the version number of the deprecated library.
-    {
-      pack: 'backbone',
-    },
     {
       pack: 'css.escape',
       folder: 'css-escape',
@@ -179,10 +175,6 @@ const assetsFolder = `${coreFolder}/assets/vendor`;
       library: 'internal.underscore',
       files: ['underscore-min.js', 'underscore-min.js.map'],
     },
-    // Only used to update the version number of the deprecated library.
-    {
-      pack: 'underscore',
-    },
     {
       pack: 'loadjs',
       files: [{ from: 'dist/loadjs.min.js', to: 'loadjs.min.js' }],