Fix flaky maxConcurrency test check

Author: alextwoods

services-custom/s3-transfer-manager/src/test/java/software/amazon/awssdk/transfer/s3/internal/UploadDirectoryHelperTest.java

@@ -561,7 +561,7 @@ void uploadDirectory_customMaxConcurrency_shouldLimitConcurrentOperations() thro
         assertThat(observedPeak)
             .as("Implementation allowed %d concurrent operations but was configured for %d", 
                 observedPeak, configuredMaxConcurrency)
-            .isEqualTo(configuredMaxConcurrency);
+            .isLessThanOrEqualTo(configuredMaxConcurrency);
 
         // Release the phase to let operations complete
         phaser.arriveAndDeregister();