[436077] Remove sample modeler's wizard and doc

Their presence can be confusing when both this example and Ecore Tools
2.0 are installed, and with the new Sirius-based Ecore Tools,
org.eclipse.sirius.sample.ecore.design is only useful as an example and
does not need these integration features.

Bug: 436077
Change-Id: Ic70a45b3adb4a2c7b4b2c29ebae1dd2c4e50408f
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>