Daft: fix cleanProjection (used by Draft_Shape2DView and DXF export)

[Roy-043]

This fixes the bug where straight edges were missing from tessellated Shape2DViews. The code was also simplified.

Forum topic: https://forum.freecadweb.org/viewtopic.php?f=23&t=58975

Thank you for creating a pull request to contribute to FreeCAD! To ease integration, we ask you to conform to the following items. Pull requests which don't satisfy all the items below might be rejected. If you are in doubt with any of the items below, don't hesitate to ask for help in the FreeCAD forum!

• Your pull request is confined strictly to a single module. That is, all the files changed by your pull request are either in App, Base, Gui or one of the Mod subfolders. If you need to make changes in several locations, make several pull requests and wait for the first one to be merged before submitting the next ones
• In case your pull request does more than just fixing small bugs, make sure you discussed your ideas with other developers on the FreeCAD forum
• Your branch is rebased on latest master git pull --rebase upstream master
• All FreeCAD unit tests are confirmed to pass by running ./bin/FreeCAD --run-test 0
• All commit messages are well-written ex: Fixes typo in Draft Move command text
• Your pull request is well written and has a good description, and its title starts with the module name, ex: Draft: Fixed typos
• Commit messages include issue #<id> or fixes #<id> where <id> is the FreeCAD bug tracker issue number in case a particular commit solves or is related to an existing issue on the tracker. Ex: Draft: fix typos - fixes #0004805

And please remember to update the Wiki with the features added or changed once this PR is merged.
Note: If you don't have wiki access, then please mention your contribution on the 0.20 Changelog Forum Thread.

---

[chennes]

@berndhahnebach CI doesn't seem to have triggered on this one...

[freecadci]

for feature branch PR_5114. Pipeline #389509856 was triggered at 7da4273. All CI branch pipelines.

[luzpaz]

@chennes can you modify the history to fix the typo of the git commit from Daft to Draft ? 🤕

[chennes]

Haha, I kind of like "daft"! Joking aside, it's a bad idea to force-push onto the main development branch, too many people will have copies with the old commit, which causes confusion later when that commit is missing from the depot.

[luzpaz]

Bummer that there is not other case scenario that makes that possible without disrupting other forks. Thanks for the follow-up 😉