Tests: Clarify the course of actions when touching tst_toolsupport

Change-Id: Ifc9caa8f1b05cd642c1bb57b0f37866de97ca2c2
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

tests/auto/other/toolsupport/tst_toolsupport.cpp

@@ -36,6 +36,10 @@
 // the TypeInformationVersion field in src/corelib/global/qhooks.cpp
 // in the same commit as the modification to the private class.
 //
+// Please also notify downstream users of the information checked here
+// such as Qt Creator developers, of such a change by putting them
+// on Cc: on the respective change on gerrit.
+//
 
 
 // Don't do this at home. This is test code, not production.