[KYUUBI #1470] Git ignore kyuubi-server metrics

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### _Why are the changes needed?_
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Make git ignore `/kyuubi-server/metrics`

### _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

- [X] [Run test](https://kyuubi.readthedocs.io/en/latest/develop_tools/testing.html#running-tests) locally before make a pull request

Closes #1470 from hddong/ignore.

Closes #1470

bf0c073 [hongdongdong] Git ignore kyuubi-server metrics

Authored-by: hongdongdong <hongdongdong@cmss.chinamobile.com>
Signed-off-by: Kent Yao <yao@apache.org>

.gitignore

@@ -70,6 +70,7 @@ embedded_zookeeper/
 /work/
 /docs/_build/
 /kyuubi-common/metrics/
+/kyuubi-server/metrics/
 **/operation_logs/
 **/server_operation_logs/
 **/engine_operation_logs/