vega-embed 6.28 breaks nimbus-yarn-ui for development

[brennie]

#11736 broke the local development environment. See logs:

yarn-nimbus-ui-1      | Failed to compile.
yarn-nimbus-ui-1      |
yarn-nimbus-ui-1      | /experimenter/node_modules/vega-embed/build/vega-embed.module.js 2477:32
yarn-nimbus-ui-1      | Module parse failed: Unexpected token (2477:32)
yarn-nimbus-ui-1      | File was processed with these loaders:
yarn-nimbus-ui-1      |  * ../../node_modules/react-scripts/node_modules/babel-loader/lib/index.js
yarn-nimbus-ui-1      | You may need an additional loader to handle the result of these loaders.
yarn-nimbus-ui-1      | | // For backwards compatibility with Vega-Lite before v4.
yarn-nimbus-ui-1      | | const w = typeof window !== 'undefined' ? window : undefined;
yarn-nimbus-ui-1      | > if (vegaLite === undefined && w?.vl?.compile) {
yarn-nimbus-ui-1      | |   vegaLite = w.vl;
yarn-nimbus-ui-1      | | }

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