Fix Data.Dict.max_by after Vim v9.1.1684

cause: vim/vim@3b3b936
Convert values pass to max() from String to Number.

Author: thinca

autoload/vital/__vital__/Data/Dict.vim

@@ -98,7 +98,7 @@ endfunction
 
 function! s:_max_by(dict, expr) abort
   let dict = s:swap(map(copy(a:dict), a:expr))
-  let key = dict[max(keys(dict))]
+  let key = dict[max(map(keys(dict), 'v:val + 0'))]
   return [key, a:dict[key]]
 endfunction