build(rxjs): updating rxjs to v7

[dvoegelin]

Description

updated rxjs from v6 to v7.5.4 due to alleged huge performance increase. https://twitter.com/benlesh/status/1491544862403006464 https://github.com/ReactiveX/rxjs/pull/6815

Verify that...

• [ ] Any related demos were added and npm start and npm run build still works
• [ ] New demos work in Safari, Chrome and Firefox
• [ ] npm run lint passes
• [ ] npm test passes and code coverage is increased
• [ ] npm run build still works

Bullhorn Internal Developers

• [ ] Run Novo Automation

Screenshots

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