[shellprocess] Reduce warnings

- The old-style cast still causes a warning, but do the
   more idiomatic (void) rather then casting to (void*)

src/modules/shellprocess/Tests.cpp

@@ -176,9 +176,9 @@ script:
 )" ) ).toMap().value( "script" );
 
     if ( !Calamares::JobQueue::instance() )
-        (void *)new Calamares::JobQueue( nullptr );
+        (void)new Calamares::JobQueue( nullptr );
     if ( !Calamares::Settings::instance() )
-        (void *)new Calamares::Settings( QString(), true );
+        (void)new Calamares::Settings( QString(), true );
 
     Calamares::GlobalStorage* gs = Calamares::JobQueue::instance()->globalStorage();
     QVERIFY( gs != nullptr );