Fix FileUpload test

[diversemix]

For Norris

[norisalsaadie]

Testing using ApolloClient and ApolloClientUpload in a server environment is not so straight forward as the library relies on a browser context, as suspected. Though some end to end testing would be useful to ensure functionality works across browsers etc.

It makes sense to revert to using a simple HTTP library like fetch or axios. For now, I'll revert this single test upload test in question.