Bug 576496: Platform documentation shows outdated screenshots

Delete screenshots when you don't add much value.

Change-Id: Ic71e684415b0cd1ba1f9af9384bd0a9a446850e3
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.common/+/186591
Tested-by: Matthias Becker <ma.becker@sap.com>
Reviewed-by: Matthias Becker <ma.becker@sap.com>