688f6ec8d7
mkEnableOption already adds "Whether to enable" and ends with a ".", so remove that duplication from the help text. Also reword it slightly while at it. (cherry picked from commit 5d3dca497ba7d20c662e8144c0bedb69433a9e4a)
*** NixOS *** NixOS is a Linux distribution based on the purely functional package management system Nix. More information can be found at https://nixos.org/nixos and in the manual in doc/manual.