Skip buffered splitatble request body for sync tests since sync client doesn't support them (#6509)

Author: zoewangg

test/s3-tests/src/it/java/software/amazon/awssdk/services/s3/regression/upload/UploadStreamingRegressionTesting.java

@@ -244,6 +244,8 @@ protected TestRequestBody getRequestBody(BodyType bodyType, ContentSize contentS
             case BLOCKING_INPUT_STREAM:
             case BLOCKING_OUTPUT_STREAM:
             case INPUTSTREAM_NO_LENGTH:
+            case BUFFERED_SPLITTABLE_KNOWN_CONTENT_LENGTH:
+            case BUFFERED_SPLITTABLE_UNKNOWN_CONTENT_LENGTH:
                 Assumptions.abort("Test BodyType not supported for sync client: " + bodyType);
             default:
                 throw new RuntimeException("Unsupported body type: " + bodyType);