Fuzzing: Add comment how to recude noise in iccparser's fuzzer

With logging enabled, all the output will slow down
execution and fill up your hard disc in about a day.

Task-number: QTBUG-79050
Change-Id: I5dcac2f349f7dbe471a5e6dd7006b89d312aeeaf
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

tests/libfuzzer/gui/iccparser/main.cpp

@@ -29,6 +29,10 @@
 #include <QGuiApplication>
 #include <QColorSpace>
 
+// Run this with
+// QT_LOGGING_RULES="qt.gui.icc=false"
+// to reduce noise and increase speed.
+
 extern "C" int LLVMFuzzerTestOneInput(const char *data, size_t size) {
     static int c = 0;
     static QGuiApplication a(c, nullptr);