clanCore/packages.nix: add gitMinimal

WIthout this, deployment via `clan machines update` will fail on the remote machine if the flake.nix has a git input

nixosModules/clanCore/packages.nix

@@ -1,11 +1,13 @@
 { pkgs, ... }:
 {
-  # essential debugging tools for networked services
   environment.systemPackages = [
+    # essential debugging tools for networked services
     pkgs.dnsutils
     pkgs.tcpdump
     pkgs.curl
     pkgs.jq
     pkgs.htop
+    # needed to deploy via `clan machines update` if the flake has a git input
+    pkgs.gitMinimal
   ];
 }