Revert "Bug 1073264 - allow attachment download to be offloaded to the webserver using X-SendFile or equivalent. r=gerv, a=glob." Morning brain thought this bug was approved for 5.0.

This reverts commit 55e8faeed19ff618483cb5803847bdba6c80c752.
Bug 1088399 - Add support for Github pull requests in See Also field. r=gerv, a=glob.