fix: revert buffers previewer (#1400)

* Reverts #1120 many issues arise (mru, highlighting, settings inheritance, ...) when previewing actual buffers

lua/telescope/builtin/internal.lua

@@ -779,18 +779,9 @@ internal.buffers = function(opts)
       results = buffers,
       entry_maker = opts.entry_maker or make_entry.gen_from_buffer(opts),
     },
-    previewer = previewers.buffers.new(opts),
+    previewer = conf.grep_previewer(opts),
     sorter = conf.generic_sorter(opts),
     default_selection_index = default_selection_idx,
-    attach_mappings = function(_, _)
-      action_set.select:enhance {
-        post = function()
-          local selection = action_state.get_selected_entry()
-          vim.api.nvim_win_set_cursor(0, { selection.lnum, selection.col or 0 })
-        end,
-      }
-      return true
-    end,
   }):find()
 end