Reduce function call overhead

The arg() function of the QString class has a variable length argument
which allows to reduce the number of chained calls to the same function.
With proper formatting, readability is not affected.

src/cli/Extract.cpp

@@ -77,7 +77,7 @@ int Extract::execute(const QStringList& arguments)
         auto fileKey = QSharedPointer<FileKey>::create();
         QString errorMsg;
         if (!fileKey->load(keyFilePath, &errorMsg)) {
-            err << QObject::tr("Failed to load key file %1: %2").arg(keyFilePath).arg(errorMsg) << endl;
+            err << QObject::tr("Failed to load key file %1: %2").arg(keyFilePath, errorMsg) << endl;
             return EXIT_FAILURE;
         }