Update test

Author: alextwoods

core/sdk-core/src/test/java/software/amazon/awssdk/core/internal/async/FileAsyncRequestBodySplitHelperTest.java

@@ -92,8 +92,8 @@ private static Runnable verifyConcurrentRequests(FileAsyncRequestBodySplitHelper
             if (concurrency > maxConcurrency.get()) {
                 maxConcurrency.set(concurrency);
             }
-            assertThat(concurrency).isLessThan(10);
-            assertThat(concurrency).isGreaterThanOrEqualTo(0);
+            assertThat(helper.numAsyncRequestBodiesInFlight()).isLessThan(10);
+            assertThat(helper.numAsyncRequestBodiesInFlight()).isGreaterThanOrEqualTo(0);
         };
     }
 }