neovim: switch nix-shell plugin back to the old way

hosts/common/programs/neovim/plugins.nix

@@ -192,8 +192,9 @@ with pkgs.vimPlugins;
     plugin = nvim-treesitter.withPlugins (_: (lib.filter (p: p.pname != "unison-grammar") nvim-treesitter.allGrammars) ++ [
       # XXX: this is apparently not enough to enable syntax highlighting!
       # nvim-treesitter ships its own queries which may be distinct from e.g. helix.
-      # the queries aren't included when i ship the grammar in this manner
-      pkgs.tree-sitter-nix-shell.nvimPlugin
+      # the queries aren't included when i ship the grammar in this manner.
+      # maybe check: <https://github.com/nvim-treesitter/nvim-treesitter/wiki/Extra-modules-and-plugins> ?
+      pkgs.tree-sitter-nix-shell
     ]);
     type = "lua";
     config = ''