labeler: don't use path-based labeling for BSD
labeler: don't use path-based labeling for BSD

ofborg labels the bsd and darwin platforms based on the title, which
conflicts with the labeler action's `sync-labels` setting (if no paths
are changed, it'll remove the label).

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs