ProjectExplorer: Remove BuildStepConfigWidget

After the previous changes it was only an empty wrapper around QWidget.

Change-Id: I58dcd82d8342c7de5e2df537044f6cf3de878a67
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/remotelinux/makeinstallstep.cpp

@@ -120,8 +120,9 @@ QString MakeInstallStep::displayName()
     return tr("Install into temporary host directory");
 }
 
-BuildStepConfigWidget *MakeInstallStep::createConfigWidget()
+QWidget *MakeInstallStep::createConfigWidget()
 {
+    // Note: this intentionally skips the MakeStep::createConfigWidget() level.
     return BuildStep::createConfigWidget();
 }