git: remove delta configuration

delta is an extra package, makes the config weird,
and makes it difficult to copy diffs to share.

defaults/git.nix

@@ -8,16 +8,10 @@
 let
   name = "git";
   cfg = config.nixowos.defaults.${name};
-  superCfg = config.programs.${name};
 in
 {
   options = {
     nixowos.defaults.${name}.enable = lib.mkEnableOption name;
-
-    # FIXME: this doesn't really belong in defaults/
-    programs.${name}.delta.enable = lib.mkEnableOption "delta within git" // {
-      default = true;
-    };
   };
 
   config = lib.mkIf cfg.enable {
@@ -38,13 +32,7 @@ in
 
         merge.conflictStyle = "zdiff3"; # easiest to understand style
         commit.verbose = true; # show diffs in commit editor
-      }
+      };
-      // (lib.optionalAttrs (superCfg.delta.enable && config.nixowos.allowAddingPackages) {
-        core.pager = "${lib.getExe pkgs.delta}";
-        interactive.diffFilter = "${lib.getExe pkgs.delta} --color-only";
-        delta.navigate = true; # use n and N to move between diff sections
-        delta.diff-highlight = true; # simpler mode, highlights inter-line changes
-      });
     };
 
   };