[DSE Solution Conversion - Platform Exploration] Remove transformation-only specification

When exporting a platform architecture, one of the additionally introduced specifications to denote template elements was not removed correctly.
Due to the recent updates to the service, this causes a transformation failure now: Checks are performed whether any of the transformation-only annotations are still present in the models that are exported back to the source AF3 project.

(from redmine: issue id 3875, created on 2019-11-27, closed on 2019-11-27)