emacsWithPackages: do not add the wrapper path twice

"$out/share/emacs/site-lisp" is added to load-path in wrapper.sh[1]
using EMACSLOADPATH and "$out/share/emacs/native-lisp/" is added to
native-comp-eln-load-path in wrapper.sh[2] using
EMACSNATIVELOADPATH. There is no point to add them again here.

Additionally, the trailing "/" in "$out/share/emacs/native-lisp/"
causes duplicate entries in native-comp-eln-load-path:

("/nix/store/hash1-emacs-packages-deps/share/emacs/native-lisp/" ; [3]
 "/home/user/.emacs.d/eln-cache/"
 "/nix/store/hash1-emacs-packages-deps/share/emacs/native-lisp"  ; [2]
 "/nix/store/hash2-emacs-29.1-rc1/lib/emacs/29.1/native-lisp/")

load-path does not change with this patch applied.

[1]: https://github.com/NixOS/nixpkgs/blob/1476c13422db64b12ee879e4f8715ccac3240285/pkgs/build-support/emacs/wrapper.sh#L47
[2]: https://github.com/NixOS/nixpkgs/blob/1476c13422db64b12ee879e4f8715ccac3240285/pkgs/build-support/emacs/wrapper.sh#L50
[3]: https://github.com/NixOS/nixpkgs/blob/1476c13422db64b12ee879e4f8715ccac3240285/pkgs/build-support/emacs/wrapper.nix#L166

pkgs/build-support/emacs/wrapper.nix

@@ -160,11 +160,9 @@ runCommand
         cat >"$siteStart" <<EOF
         (let ((inhibit-message t))
           (load-file "$emacs/share/emacs/site-lisp/site-start.el"))
-        (add-to-list 'load-path "$out/share/emacs/site-lisp")
+        ;; "$out/share/emacs/site-lisp" is added to load-path in wrapper.sh
+        ;; "$out/share/emacs/native-lisp" is added to native-comp-eln-load-path in wrapper.sh
         (add-to-list 'exec-path "$out/bin")
-        ${lib.optionalString withNativeCompilation ''
-          (add-to-list 'native-comp-eln-load-path "$out/share/emacs/native-lisp/")
-        ''}
         ${lib.optionalString withTreeSitter ''
           (add-to-list 'treesit-extra-load-path "$out/lib/")
         ''}