[KYUUBI #2973] Decorate LOG in the RetryableRestClient with static final

### _Why are the changes needed?_

A minor  improvement by using static.

### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible

- [ ] Add screenshots for manual tests if appropriate

- [ ] [Run test](https://kyuubi.apache.org/docs/latest/develop_tools/testing.html#running-tests) locally before make a pull request

Closes #2973 from zhaomin1423/fix_log.

Closes #2973

285ac0a [Min Zhao] Decorate LOG in the RetryableRestClient with static final

Authored-by: Min Zhao <zhaomin1423@163.com>
Signed-off-by: Cheng Pan <chengpan@apache.org>

Author: zhaomin1423

kyuubi-rest-client/src/main/java/org/apache/kyuubi/client/RetryableRestClient.java

@@ -34,7 +34,7 @@
  */
 public class RetryableRestClient implements InvocationHandler {
 
-  private Logger LOG = LoggerFactory.getLogger(RetryableRestClient.class);
+  private static final Logger LOG = LoggerFactory.getLogger(RetryableRestClient.class);
 
   private final RestClientConf conf;
   private final List<String> uris;