Remove redundant loading of init.el in home-manager installation instructions

The home-manager already does this, which causes `init.el` to be loaded twice if the user also adds this snippet to their config.

README.md

@@ -33,9 +33,6 @@ let
   };
 in {
   home.packages = [ doom-emacs ];
-  home.file.".emacs.d/init.el".text = ''
-      (load "default.el")
-  '';
 }
 ```