refactor(git.nix): drop redundant gh and duplicate tea packages

programs.gh.enable (in shell.nix) already installs gh, so the explicit
pkgs.gh was redundant. pkgs.tea was also declared in shell.nix; keep the
single declaration there and remove the duplicate here.

lyrathorpe/home/git.nix

@@ -12,8 +12,6 @@ in
 {
   home.packages = [
     pkgs.commitizen
-    pkgs.gh
-    pkgs.tea
   ];
 
   programs.git = {