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>

doc/nuwiki.txt

@@ -122,7 +122,6 @@ default): >
         template_default = 'default',
         css_name         = 'style.css',
         auto_export      = false,
-        nested_syntaxes  = { python = 'python' },
       },
     },
   })
@@ -196,11 +195,11 @@ match upstream vimwiki.
 `exclude_files`          List of glob patterns excluded from export.
 `listsyms`               `' .oOX'` — checkbox progression characters.
 `listsyms_propagate`     `true`
-`maxhi`                  `1` — inline heading-level highlighting count.
-`nested_syntaxes`        `{}` — embed other syntaxes inside
-                         `{{{lang …}}}` fenced blocks.
 `links_space_char`       `' '`
 
+Code fences tagged with a language (`{{{python …}}}`) are highlighted with
+that language's syntax automatically — there is no `nested_syntaxes` key.
+
 Vim-specific globals ~
 
                                                   *g:nuwiki_no_default_mappings*