Fix a typo and use proper deprecation notification system

Fix a typo pointed out by @thecow275.

Also, use the deprecated notification system which respects the
deprecated_lua_api_handling setting.

builtin/mainmenu/tab_texturepacks.lua

@@ -73,7 +73,7 @@ local function get_formspec(tabview, name, tabdata)
  if not file_exists(infofile) then
  infofile = current_texture_path .. DIR_DELIM .. "info.txt"
  if file_exists(infofile) then
- core.log("info.txt is depreciated. description.txt should be used instead.")
+ core.log("deprecated", "info.txt is deprecated. description.txt should be used instead.")
  end
  end