- Remove deprecated navigator.platform API usage
- Remove unused variables: browserLanguage, platform, timeZoneOffset
- Clean up dead code in taxReturnCreate.ts and PreviewTaxReturns.tsx
These variables were declared but never used in the request bodies, creating unnecessary code clutter. The navigator.platform API is also deprecated according to MDN documentation.
This change improves code maintainability and eliminates deprecation warnings without affecting functionality.