Remove setting referrer from HttpFunctions

It was introduced in 5d210b50 but no callers have ever been updated
so this always falls back on $wgTitle (which is usually wrong). It
only works on cURL, and is marginally useful at best.

Change-Id: Ic498108af9f466cefbd0072f94f0efa4055cd169
Merge "Remove setting referrer from HttpFunctions"