Remove file TODOPORT

Summary:
This is the latest status of the items on the now deleted list:

- 2007: SOMETIMES BUTTONS IN MAIN DIALOG MAKE KSUDOKU CRASH
    - 2018: Is this still an issue?
- 2007: export system
    - 2018: What is meant by that?
- 2007: status bar text disappear sometimes
    - 2018: Is this still an issue?
- 2007: flickering
    - 2018: Is this still an issue?
- 2007: knewstuff crashes
    - 2018: Where is this used?
- 2007: KConfig
    - 2018: Is this still an issue?

Reviewers: #kde_games

Subscribers: aacid, kde-games-devel

Differential Revision: https://phabricator.kde.org/D12900