[chore] NewsDownloader: various minor string fixes (#8268)

Follow-up to <https://github.com/koreader/koreader/pull/8267>.

plugins/newsdownloader.koplugin/main.lua

@@ -308,7 +308,7 @@ review your feed configuration file.]])
     if touchmenu_instance then
         -- Ask the user if they want to go to their downloads folder
         -- or if they'd rather remain at the menu.
-        feed_message = feed_message .. _("Go to downloaders folder?")
+        feed_message = feed_message .. _("Go to download folder?")
         local should_go_to_downloads = UI:confirm(
             feed_message,
             _("Close"),
@@ -677,7 +677,7 @@ function NewsDownloader:viewFeedList()
         UIManager:close(self.kv)
     end
     self.kv = KeyValuePage:new{
-        title = _("RSS/Atom Feeds List"),
+        title = _("RSS/Atom feeds"),
         value_overflow_align = "right",
         kv_pairs = view_content,
         callback_return = function()
@@ -972,7 +972,7 @@ end
 
 function NewsDownloader:saveConfig(config)
     local UI = require("ui/trapper")
-    UI:info(_("Saving news feed list..."))
+    UI:info(_("Saving news feed list…"))
     local persist = Persist:new{
         path = self.feed_config_path
     }