update example for waitforcallback

Author: zhongkechen

examples/src/main/java/software/amazon/lambda/durable/examples/callback/WaitForCallbackFailedExample.java

@@ -32,11 +32,10 @@ public String handleRequest(ApprovalRequest input, DurableContext context) {
                                     .serDes(new FailedSerDes())
                                     .build())
                             .build());
-        } catch (Exception ex) {
+        } catch (SuspendExecutionException e) {
             // not to swallow the SuspendExecutionException
-            if (ex instanceof SuspendExecutionException suspendExecutionException) {
-                throw suspendExecutionException;
-            }
+            throw e;
+        } catch (Exception ex) {
             return ex.getClass().getSimpleName() + ":" + ex.getMessage();
         }