Update WritersCanShare to False doesn't work

[AlvarDev]

In google.golang.org/api/drive/v3

I'm translating an app from Python to Go, but I have an issue with WritersCanShare update:

• WritersCanShare = true works, the file property is updated from false to true

• WritersCanShare = false doesn't work, the file property never changes

[shantuo]

Hi there, this is the issue tracker for the website godoc.org, please file issue against their repo instead.