winmm: Fix handle leak in timer tests.

dlls/winmm/tests/timer.c

diff --git a/dlls/winmm/tests/timer.c b/dlls/winmm/tests/timer.c
index 7ac86b9..be63f6b 100644
--- a/dlls/winmm/tests/timer.c
+++ b/dlls/winmm/tests/timer.c
@@ -190,6 +190,7 @@
            "thread priority is %s, should be THREAD_PRIORITY_TIME_CRITICAL\n",
            get_priority(priority));
     }
+    timeKillEvent(id);
 }
 
 START_TEST(timer)