QTRY_IMPL: revert an incorrect change to a code comment

The comment in the QTRY_IMPL macro definition pertains to the
following using namespace std::chrono_literals, which has nothing to
do with the default timeout of QTRY_ macros, because that is
determined somewhere else. Further, "5 seconds" is not a valid chrono
literal, as "5s" was.

Partially reverts 55f163382d36ddf908fc2884f2020a1b92340c10.

Found in API-review.

Change-Id: Ic1242436bf87d7067e3c5240eb2687505e24800f
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
(cherry picked from commit 270b2194106224c0dfb2221bcd85676a747b4f13)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/testlib/qtestcase.h

@@ -193,7 +193,7 @@ inline void useVerifyThrowsException() {}
 
 #define QTRY_IMPL(expr, timeoutAsGiven)\
     const auto qt_test_timeoutAsMs = [&] { \
-            /* make 5 seconds (by default) work without user action: */ \
+            /* make 5s work w/o user action: */ \
             using namespace std::chrono_literals; \
             return std::chrono::milliseconds{timeoutAsGiven}; \
         }(); \