Remove "move zoomed area" shortcuts by default

Summary: This is a follow-up for D11377, as requested by @graesslin. The patch removes the default shortcuts for the {nav Move zoomed area} actions.

Test Plan:
Deployed KWin with patch, killed and restarted KWin, created and logged into new user account, then zoomed in:
- {key Meta Ctrl Arrows} do not move the zoomed view
- The actions are still visible (without shortcuts) in {nav System Settings > Shortcuts > Global Shortcuts > KWin}
- You can still set custom shortcuts for the actions, and they work

Reviewers: #kwin, graesslin

Reviewed By: #kwin, graesslin

Subscribers: graesslin, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D11526