uic: Fix clazy warnings clazy-qstring-left, clazy-unused-non-trivial-variable

Change-Id: Ibbb9a85dba7773bb70298906bc370b4e24d7d901
Reviewed-by: Robert Loehning <robert.loehning@qt.io>
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/tools/uic/cpp/cppwritedeclaration.cpp

@@ -71,7 +71,6 @@ void WriteDeclaration::acceptUI(DomUI *node)
     QString className = qualifiedClassName;
 
     m_driver->findOrInsertWidget(node->elementWidget());
-    QString widgetClassName = node->elementWidget()->attributeClass();
 
     QString exportMacro = node->elementExportMacro();
     if (!exportMacro.isEmpty())

src/tools/uic/cpp/cppwriteinitialization.cpp

@@ -1265,7 +1265,7 @@ void WriteInitialization::writeProperties(const QString &varName,
 
         if (stdset) {
             setFunction = QLatin1String("->set")
-                        + propertyName.left(1).toUpper()
+                        + propertyName.at(0).toUpper()
                         + propertyName.midRef(1)
                         + QLatin1Char('(');
         } else {