Use qputenv instead of (not existing) qsetenv in outcommented code

Could you please change lines 55 and 56 in file https://github.com/qtproject/qtquickcontrols2/blob/5.6/tests/manual/testbench/main.cpp from

// qsetenv("QT_QUICK_FILE_SELECTORS", "material");
// qsetenv("QT_LABS_CONTROLS_STYLE", "material");

to

// qputenv("QT_QUICK_FILE_SELECTORS", "material");
// qputenv("QT_LABS_CONTROLS_STYLE", "material");

There is no command "qsetenv", it is "qputenv".