git mv ENVIRONMENT_VARS to platform-ui

... gathering env vars in a shared utility package was too cute. revert
back to:
- gather env data from end application bundle
- feed env data to shared packages at import / runtime

Author: NiloCK

packages/common/src/index.ts

@@ -1,6 +1,5 @@
 export * from './wire-format.js';
 export * from './course-data.js';
-export { default as ENV } from './ENVIRONMENT_VARS.js';
 export * from './elo.js';
 export * from './namespacer.js';
 export * from './logshim.js';