Stop Q_AUTOTEST_EXPORTing QKeyBinding and QKeySequencePrivate

The QKeySequence test no longer uses private members (since commit
725bdc3f

), so that is no longer needed.

Also, remove the unused include from the test.

Change-Id: I4d252bb3efd7282f74c44e48444c23ab51d48ea5
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>