fix(color): follow linked hl groups

Without 'link = false' (default is true), the returned attributes are
the ones of the source highlight group, not of the target highlight
group. This behaviour doesn't match the way Neovim renders highlighted
text.

lua/bufferline/colors.lua

@@ -48,7 +48,7 @@ end
 local new_hl_api = api.nvim_get_hl ~= nil
 local get_hl = function(name, use_cterm)
   if new_hl_api then
-    local hl = api.nvim_get_hl(0, { name = name })
+    local hl = api.nvim_get_hl(0, { name = name, link = false })
     if use_cterm then
       hl.fg, hl.bg = hl.ctermfg, hl.ctermbg
     end