nixos/neovim: fix remote plugin manifest generation (#191852)

Stops using ex mode when running neovim for remote plugin manifest generation, since that leads to errors in more recent neovim versions with various plugins.
neovim commit that breaks this plugin generation: neovim/neovim@64d147b

pkgs/applications/editors/neovim/wrapper.nix

@@ -100,7 +100,7 @@ let
         if ! $out/bin/nvim-wrapper \
           -u ${writeText "manifest.vim" manifestRc} \
           -i NONE -n \
-          -E -V1rplugins.log -s \
+          -V1rplugins.log \
           +UpdateRemotePlugins +quit! > outfile 2>&1; then
           cat outfile
           echo -e "\nGenerating rplugin.vim failed!"