fix: Add flush() calls in samples (#1116)

* fix: Add flush() calls in samples

* Add optional in comment

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Author: losalex

samples/snippets/src/main/java/com/example/logging/QuickstartSample.java

@@ -53,6 +53,9 @@ public static void main(String... args) throws Exception {
 
       // Writes the log entry asynchronously
       logging.write(Collections.singleton(entry));
+
+      // Optional - flush any pending log entries just before Logging is closed
+      logging.flush();
     }
     System.out.printf("Logged: %s%n", textPayload);
   }

samples/snippets/src/main/java/com/example/logging/WriteLogEntry.java

@@ -45,7 +45,11 @@ public static void main(String[] args) throws Exception {
               .setResource(MonitoredResource.newBuilder("global").build())
               .build();
 
+      // Writes the log entry asynchronously
       logging.write(Collections.singleton(entry));
+
+      // Optional - flush any pending log entries just before Logging is closed
+      logging.flush();
     }
     System.out.printf("Wrote to %s\n", logName);
   }