Remove an unused constant defined in tst_QDate

Change-Id: If00abed2aec9bf8f1d88ff4915c60a3e6e9dc74e
Reviewed-by: Tatiana Borisova <tatiana.borisova@qt.io>
Reviewed-by: Magdalena Stojek <magdalena.stojek@qt.io>

tests/auto/corelib/time/qdate/tst_qdate.cpp

@@ -552,11 +552,9 @@ void tst_QDate::startOfDay_endOfDay_data()
 #if QT_CONFIG(timezone) && QT_CONFIG(timezone_tzdb) && defined(__GLIBCXX__)
     // The IANA-DB parser in libstdc++ (at least up to _GLIBCXX_RELEASE == 14) gets
     // a lot of zone-transitions wrong in C++20's tzdb :-(
-    constexpr BackendKludges GlibCxxNoStart = IgnoreStart;
     constexpr BackendKludges GlibCxxNoBoth = IgnoreBoth;
 #define KLUDGING
 #else
-    constexpr BackendKludges GlibCxxNoStart = Clean;
     constexpr BackendKludges GlibCxxNoBoth = Clean;
 #endif
     const QTimeZone UTC(QTimeZone::UTC);