Correct parameter handling in Go example generation script

[justinpolygon]

What was changed

• Fixed zero-parameter endpoints (e.g. GetMarketHolidaysWithResponse, GetMarketStatusWithResponse):
  • No more unused gen import
  • Correct call syntax (no syntax error on newline)
• Made every WithResponse(...) call consistently multiline (including zero-param cases) so your token-replacement logic works everywhere
• All previous fixes (enum typing, real OpenAPI values vs TOKEN_, etc.) preserved

Result
All generated examples now compile cleanly and look uniform across the entire client.