Suspend distribution of Confluence publisher plugin

* Suspend Confluence publisher plugin distribution - uses closed source dependency

jenkins-infra/helpdesk#3856 explains that the
Confluence publisher plugin uses a dependency that is not open source
licensed.

The Confluence publisher libraries are Atlassian licensed including:

* com.atlassian.confluence:confluence-java-api:7.14.0
* com.atlassian.confluence:confluence-rest-client:7.14.0
* com.atlassian.confluence:confluence-rest-serialization:7.14.0
* com.atlassian.confluence:confluence-rest-api:7.14.0

The Atlassian license is not an open source license.  Refer to
https://www.atlassian.com/legal/software-license-agreement for the
details of the license.

https://www.jenkins.io/project/governance/#license says that the Jenkins
project requires plugins that it distributes to be open source, including
their dependencies.  When a closed source dependency is detected in a
plugin, we suspend distribution of that plugin.  If maintainers update
the plugin to remove the closed source dependency, distribution can
begin for the new release that removes the closed source dependency.

Fixes jenkins-infra/helpdesk#3856

resources/artifact-ignores.properties

@@ -895,3 +895,6 @@ batch-task@1.19               # SECURITY-1025
 #   https://github.com/jenkins-infra/helpdesk/issues/3842#issuecomment-1847399101
 #   https://github.com/jenkins-infra/helpdesk/issues/3842#issuecomment-1847559631
 crowd2 = https://github.com/jenkins-infra/helpdesk/issues/3854
+
+# Non-open source dependency
+confluence-publisher = https://github.com/jenkins-infra/helpdesk/issues/3856