Disable service worker initializer

[tgxworld (Alan Tan)]

@Jacky_Cheng

I forgot to bring up that Safari now can support service-worker.

Yup we know but Discourse is not ready to support Service workers on Safari yet because it has been problematic for us so far.

@Jacky_Cheng

the else condition would also unregister service worker, it should add the url condition.

It does consider the URL condition because I extracted both of the unregister function calls into a common function.