Fix observationShouldNotLeakToFutureCompletionThread jdk 17 compatibility

Signed-off-by: pema4 <[email protected]>

Author: pema4

samples/micrometer-samples-spring-framework6/src/test/java/io/micrometer/samples/spring6/aop/ObservedAspectTests.java

@@ -179,7 +179,9 @@ void observationShouldNotLeakToFutureCompletionThread() {
         ObservedService service = pf.getProxy();
         FakeAsyncTask fakeAsyncTask = new FakeAsyncTask("test-result");
 
-        try (var sameThreadExecutor = new ThreadPoolExecutor(1, 1, 60, TimeUnit.SECONDS, new LinkedBlockingQueue<>())) {
+        ThreadPoolExecutor sameThreadExecutor = new ThreadPoolExecutor(1, 1, 60, TimeUnit.SECONDS,
+                new LinkedBlockingQueue<>());
+        try {
             CompletableFuture<String> asyncResult = service
                 .parent(() -> service.asyncChild(fakeAsyncTask, sameThreadExecutor));
             CompletableFuture<Void> asyncAssertion = asyncResult.thenRunAsync(
@@ -188,6 +190,9 @@ void observationShouldNotLeakToFutureCompletionThread() {
 
             assertThat(asyncAssertion).succeedsWithin(Duration.ofMillis(200));
         }
+        finally {
+            sameThreadExecutor.shutdown();
+        }
     }
 
     @Test