gh-136003: Close file descriptors in test (GH-139225)

This fixes file descriptor leaks introduced in GH-136004

Author: encukou

Lib/test/test_capi/test_misc.py

@@ -1996,6 +1996,7 @@ def test_pending_call_creates_thread_subinterpreter(self):
         def output():
             time.sleep(1)
             os.write({w}, b"x")
+            os.close({w})
 
 
         def callback():
@@ -2014,6 +2015,7 @@ def create_pending_call():
         interp.close()
         data = os.read(r, 1)
         self.assertEqual(data, b"x")
+        os.close(r)
 
 
 @requires_subinterpreters