[Fix] Removed reference to icon in PDE plugin

The Eclipse Capra UI bundle referred to an icon in org.eclipse.pde.ui
which is not a standard dependency for Capra. While this did not cause
any issues for the end users, it triggered exceptions in tests. This
commit removes the reference.
Change-Id: I634dbd97f1d68f519486d3b83af0f263aa7a4cc8
diff --git a/bundles/org.eclipse.capra.ui/plugin.xml b/bundles/org.eclipse.capra.ui/plugin.xml
index 8f97461..23a6bbf 100644
--- a/bundles/org.eclipse.capra.ui/plugin.xml
+++ b/bundles/org.eclipse.capra.ui/plugin.xml
@@ -106,7 +106,6 @@
 		<menuContribution allPopups="false"
 			locationURI="toolbar:org.eclipse.capra.ui.views.SelectionView">
 			<command commandId="org.eclipse.capra.ui.commands.createTrace"
-				disabledIcon="platform:/plugin/org.eclipse.pde.ui/icons/dlcl16/add_att.png"
 				icon="platform:/plugin/org.eclipse.ui/icons/full/obj16/add_obj.png"
 				label="%command.createtrace.name" mnemonic="%command.createtrace.mnemonic"
 				style="push" tooltip="%command.createtrace.tooltip">