tests/ptimer: Remove unnecessary inclusion of libqtest.h

ptimer-test is a unit test, not a qtest, so libqtest.h is not
required here.

Message-Id: <20191218103059.11729-3-thuth@redhat.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NThomas Huth <thuth@redhat.com>

tests/ptimer-test.c

@@ -14,7 +14,6 @@
 #include "qemu/main-loop.h"
 #include "hw/ptimer.h"
 
-#include "libqtest.h"
 #include "ptimer-test.h"
 
 static bool triggered;