Bumps [plugin](https://github.com/jenkinsci/plugin-pom) from 4.51 to 4.55.
- [Release notes](https://github.com/jenkinsci/plugin-pom/releases)
- [Changelog](https://github.com/jenkinsci/plugin-pom/blob/master/CHANGELOG.md)
- [Commits](jenkinsci/plugin-pom@plugin-4.51...plugin-4.55)

---
updated-dependencies:
- dependency-name: org.jenkins-ci.plugins:plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Bumps [git-changelist-maven-extension](https://github.com/jenkinsci/incrementals-tools) from 1.4 to 1.6.
- [Release notes](https://github.com/jenkinsci/incrementals-tools/releases)
- [Commits](jenkinsci/incrementals-tools@parent-1.4...parent-1.6)

---
updated-dependencies:
- dependency-name: io.jenkins.tools.incrementals:git-changelist-maven-extension
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

…gelist-maven-extension-1.6' into test-with-java-21

Jenkins core has required Java 11 for more than a year.

https://stats.jenkins.io/pluginversions/nexus-artifact-uploader.html shows
that 55% of installations of this plugin are already running 2.361.4 or
newer and that 92% of the installations of the most recent release (2.14)
are running 2.361.4 or newer.  Users that are upgrading this plugin are
already using Jenkins 2.361.4 or newer.

Java 21 was released Sep 19, 2023. We want to announce full support
for Java 21 in early October and would like the most used plugins to be
compiled and tested with Java 21.

The acceptance test harness and plugin bill of materials tests are already
passing with Java 21. This is a further step to improve plugin readiness
for use with Java 21 and for development with Java 21.

The change intentionally tests only two Java configurations, Java 17
and Java 21 because we believe that the risk of a regression that only
affects Java 11 is low. We generate Java 11 byte code with the Java 17
and the Java 21 builds, so we're already testing Java 11 byte code.

https://github.com/codehaus-plexus/plexus-utils/releases/tag/plexus-utils-3.5.1
notes that the changes look safe.