fix write option typo in java samples (#7894)

Summary:
this is a trivial PR for rocksdb java samples, I think it is a typo about write options. to do sync write, WAL should not be disabled

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7894

Reviewed By: jay-zhuang

Differential Revision: D26047128

Pulled By: mrambacher

fbshipit-source-id: a06ce54cb61af0d3f2578a709c34a0b1ccecb0b2

java/samples/src/main/java/RocksDBSample.java

@@ -210,7 +210,7 @@ public class RocksDBSample {
         // repeat the test with WriteOptions
         try (final WriteOptions writeOpts = new WriteOptions()) {
           writeOpts.setSync(true);
-          writeOpts.setDisableWAL(true);
+          writeOpts.setDisableWAL(false);
           db.put(writeOpts, testKey, testValue);
           len = db.get(testKey, enoughArray);
           assert (len == testValue.length);