vim-patch:9.1.1477: no easy way to deduplicate text

Problem:  no easy way to deduplicate text
Solution: add the :uniq ex command
          (Hirohito Higashi)

closes: vim/vim#17538

74f0a77bb9

Co-authored-by: Hirohito Higashi <h.east.727@gmail.com>

src/nvim/eval.lua

@@ -12835,6 +12835,7 @@ M.funcs = {
       	let newlist = uniq(copy(mylist))
       <The default compare function uses the string representation of
       each item.  For the use of {func} and {dict} see |sort()|.
+      For deduplicating text in the current buffer see |:uniq|.
 
       Returns zero if {list} is not a |List|.