zsh: do not duplicate zsh.{profile,login,logout,env}Extra in prezto (#7061)

In #7057 changed the definition of how the prezto files where loaded
(from using `.source` to `.text`) and also manually add the text from
`zsh.{profile,login,logout,env}Extra` files to the prezto definitions,
but the last part was unnecessary and now we have duplicates inside the
file.

This commit fixes it.

modules/programs/zsh/prezto.nix

@@ -13,7 +13,6 @@ let
     ;
 
   cfg = config.programs.zsh.prezto;
-  cfgZsh = config.programs.zsh;
 
   relToDotDir =
     file:
@@ -429,24 +428,20 @@ in
         home.file."${relToDotDir ".zprofile"}".text = ''
           # Generated by Nix
           source ${cfg.package}/share/zsh-prezto/runcoms/zprofile
-          ${cfgZsh.profileExtra}
         '';
         home.file."${relToDotDir ".zlogin"}".text = ''
           # Generated by Nix
           source ${cfg.package}/share/zsh-prezto/runcoms/zlogin
-          ${cfgZsh.loginExtra}
         '';
         home.file."${relToDotDir ".zlogout"}".text = ''
           # Generated by Nix
           source ${cfg.package}/share/zsh-prezto/runcoms/zlogout
-          ${cfgZsh.logoutExtra}
         '';
         # Using mkAfter to make sure we load Home-Manager's environment
         # variables first (see modules/prgrams/zsh.nix)
         home.file."${relToDotDir ".zshenv"}".text = lib.mkAfter ''
           # Generated by Nix
           source ${cfg.package}/share/zsh-prezto/runcoms/zshenv
-          ${cfgZsh.envExtra}
         '';
         home.file."${relToDotDir ".zpreztorc"}".text = ''
           # Generated by Nix