feat(lua): replace buffer with buf in vim.keymap.set/del #38360

The `buffer` option remains functional but is now undocumented.
Providing both will raise an error. Since providing `buf` was disallowed
before, there is no code that will break due to using `buffer` alongside
`buf`.

runtime/lua/vim/health.lua

@@ -505,7 +505,7 @@ function M._check(mods, plugin_names)
         if not pcall(vim.cmd.close) then
           vim.cmd.bdelete()
         end
-      end, { buffer = bufnr, silent = true, noremap = true, nowait = true })
+      end, { buf = bufnr, silent = true, noremap = true, nowait = true })
     end
   end)