Clean-up: remove unnecessary, non-externalized exception message

Change-Id: I3a2a03d6307b061e7607c5278700a09c21ec4a2f
diff --git a/org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/ModuleAttributeConfiguration.java b/org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/ModuleAttributeConfiguration.java
index 69c95a9..1e2951c 100644
--- a/org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/ModuleAttributeConfiguration.java
+++ b/org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/ModuleAttributeConfiguration.java
@@ -61,11 +61,8 @@
 
 	@Override
 	public IClasspathAttribute performEdit(Shell shell, ClasspathAttributeAccess attribute) {
-		throw new UnsupportedOperationException("should be handled specifically");
-//
-//		String initialValue= attribute.getClasspathAttribute().getValue();
-//		String newValue= TRUE.equals(initialValue) ? null : TRUE;
-//		return JavaCore.newClasspathAttribute(CPListElement.MODULE, newValue);
+		// we should not get here, because this attribute is 'builtin' for which specific handling is implemented
+		throw new UnsupportedOperationException();
 	}
 
 	@Override