[SPARK-36171][BUILD] Upgrade GenJavadoc to 0.18
[SPARK-36171][BUILD] Upgrade GenJavadoc to 0.18

### What changes were proposed in this pull request?

This PR upgrades `GenJavadoc` plugin from `0.17` to `0.18`.

### Why are the changes needed?

`0.18` includes a bug fix for `Scala 2.13`.
```
This release fixes a bug (#286) with Scala 2.13.6 in relation with deprecated annotations in Scala sources leading to a NoSuchElementException in some cases.
```
https://github.com/lightbend/genjavadoc/releases/tag/v0.18

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Built the doc for Scala 2.13.
```
build/sbt -Phive -Phive-thriftserver -Pyarn -Pmesos -Pkubernetes -Phadoop-cloud -Pspark-ganglia-lgpl -Pkinesis-asl -Pdocker-integration-tests -Pkubernetes-integration-tests -Pscala-2.13 unidoc
```

Closes #33383 from sarutak/upgrade-genjavadoc-0.18.

Authored-by: Kousuke Saruta <7d45abe39fd242ee2f6575da28f13d66568418b3@oss.nttdata.com>
Signed-off-by: Dongjoon Hyun <6ff48b33cbb828151035af58a92f18a39f1d1036@apache.org>
(cherry picked from commit ad744fb4bf4790db2c500bf905f431ccf274055a)
Signed-off-by: Dongjoon Hyun <6ff48b33cbb828151035af58a92f18a39f1d1036@apache.org>

milliman/spark,milliman/spark,milliman/spark,milliman/spark,milliman/spark,milliman/spark,milliman/spark