[KYUUBI apache#5135] [Minor] Exclude web-ui coverage reports in rat plugins

### _Why are the changes needed?_

- To avoid the generated web-ui's coverage report files triggering Rat plugin checks on Maven
```
[WARNING] Files with unapproved licenses:
  kyuubi-server/web-ui/coverage/index.html
  kyuubi-server/web-ui/coverage/locales/en_US/index.html
  kyuubi-server/web-ui/coverage/locales/zh_CN/index.html
...
[ERROR] Failed to execute goal org.apache.rat:apache-rat-plugin:0.15:check (default) on project kyuubi-parent: Too many files with unapproved license: 21 See RAT report in: /kyuubi/target/rat.txt ->
```

### _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/master/contributing/code/testing.html#running-tests) locally before make a pull request

Closes apache#5135 from bowenliang123/rat-exclude.

Closes apache#5135

1ec4411 [liangbowen] add web-ui/coverage/* to rat exclusions

Authored-by: liangbowen <liangbowen@gf.com.cn>
Signed-off-by: liangbowen <liangbowen@gf.com.cn>

Author: bowenliang123

.rat-excludes

@@ -53,6 +53,7 @@ build/scala-*/**
 **/*.sqlite.sql
 **/node/**
 **/web-ui/dist/**
+**/web-ui/coverage/**
 **/pnpm-lock.yaml
 **/node_modules/**
 **/gen/*