pythongh-109357: Fix test_monitoring.test_gh108976() (python#109358)

The test now calls free_tool_id() so it can be run multiple times in
the same process. For example, the following command no longer fails:

    python -m test test_monitoring -R 3:3

Author: vstinner

Lib/test/test_monitoring.py

@@ -1721,6 +1721,7 @@ def make_foo_optimized_then_set_event():
 
     def test_gh108976(self):
         sys.monitoring.use_tool_id(0, "test")
+        self.addCleanup(sys.monitoring.free_tool_id, 0)
         sys.monitoring.set_events(0, 0)
         sys.monitoring.register_callback(0, E.LINE, lambda *args: sys.monitoring.set_events(0, 0))
         sys.monitoring.register_callback(0, E.INSTRUCTION, lambda *args: 0)