`test/downloads.jl` tests not being run

[nickrobinson251]

This test file https://github.com/JuliaWeb/HTTP.jl/blob/master/test/download.jl is no longer being included in runtests.jl (it is commented out) https://github.com/JuliaWeb/HTTP.jl/blob/master/test/runtests.jl#L16 since da3f08e / #1065

From #1092 (comment):

The downloads tests were relying on a public server that is no longer serving requests in the same way, so they were just constantly failing, so they were disabled.