fixes #4491
Deprecation warnings should not be used in Nixpkgs because they spam innocent "nix-env -qa" users with (in this case) dozens of messages that they can't do anything about. This also reverts commit 2ca883338389b7ab995924a0cab0211993bdf1da.
Apparently everyone just copied those variables, instead of creating a library constant for them. Some even removed the comment. -.-