[summary] Prefer a step's widget over text

- the partition module makes a nice descriptive widget,
  which includes the text it **also** has for the summary;
  (the text is intended for the QML summary).
- In general, if a module has a widget for the summary, assume
  that that is the **whole** summary and use it instead of text.

This resolves duplicate summaries -- showing the text of the
partitioning-step, followed by its widget -- introduced in July.

src/modules/summary/SummaryPage.cpp

@@ -93,14 +93,14 @@ createStepWidget( const QString& description, QWidget* innerWidget, const QPalet
     CalamaresUtils::unmarginLayout( itemBodyLayout );
 
     itemBodyCoreLayout->addSpacing( CalamaresUtils::defaultFontHeight() / 2 );
-    if ( !description.isEmpty() )
-    {
-        itemBodyCoreLayout->addWidget( createBodyLabel( description, palette ) );
-    }
     if ( innerWidget )
     {
         itemBodyCoreLayout->addWidget( innerWidget );
     }
+    else
+    {
+        itemBodyCoreLayout->addWidget( createBodyLabel( description, palette ) );
+    }
 
     return w;
 }