docs(config): drop client-side keys and refresh per-wiki reference

Remove nested_syntaxes, maxhi and diary_start_week_day from the config
reference (block, tables and key lists) since the server no longer
consumes them, and note that language-tagged code fences are highlighted
automatically with no nested_syntaxes key.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lua/nuwiki/config.lua

@@ -21,13 +21,12 @@ M.defaults = {
   -- `doc/nuwiki.txt`):
   --   name, root, file_extension, syntax, index
   --   diary_rel_path, diary_index, diary_frequency,
-  --   diary_start_week_day, diary_caption_level, diary_sort,
-  --   diary_header
+  --   diary_caption_level, diary_sort, diary_header
   --   html_path, template_path, template_default, template_ext,
   --   template_date_format, css_name, auto_export, auto_toc,
   --   html_filename_parameterization, exclude_files, color_dic
-  --   maxhi, listsyms, listsyms_propagate, list_margin,
-  --   links_space_char, nested_syntaxes
+  --   listsyms, listsyms_propagate, list_margin,
+  --   links_space_char
   wikis = nil,
 
   -- Per-buffer glue. Each subgroup mirrors vimwiki's