Instance of panel "Import Workspace" present in "Not assigned panels" section

Description of problem:
There is an instance of panel "Import Workspace" present in "Not assigned panels" section of the page "Import and Export" in Showcase workspace.

Version-Release number of selected component (if applicable):
Dashbuilder DR5

How reproducible:
always

Steps to Reproduce:
1. Start the application and navigate to workspace "Showcase", page "Import and Export"

Actual results:
On the bottom of the page that there is instance of panel "Import Workspace" in "Not assigned panels" section

Expected results:
The unasigned instance of panel should be delete from the page, in the initial configuration of application.