[docs] [issue21063] Touch up one-line descriptions of modules for module index

Brett Cannon added the comment: Sure, if you are just looking for "This module" you won't find very many instances. The bug is more about doing a sweep through *every* module's synopsis and just cleaning them up to read better. The "this module" instance for linecache is just an example of why a cleanup would be good to do. ---------- _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue21063> _______________________________________