HTML report : listen on localhost

[jfgreffier]

I came across issue #11568 on my machine. I didn't realize it was fixed, even after reading the code.

This MR is for only for readibility and to harmonize with the rest of the code in httpServer.ts It follows this suggestion https://github.com/microsoft/playwright/issues/11568#issuecomment-1173566316

Also I think localhost is more universally understood than 127.0.0.1 or ::1 for users