checkUnusedConstraints fails with JavaPluginExtension does not exist (since 2.24)

[nora-h-papercut]

since #1225, checkUnusedConstraints fails with

Execution failed for task ':checkUnusedConstraints'.
> Error while evaluating property 'classpath' of task ':checkUnusedConstraints'.
   > Failed to calculate the value of task ':checkUnusedConstraints' property 'classpath'.
      > Extension of type 'JavaPluginExtension' does not exist. Currently registered extension types: [ExtraPropertiesExtension, VersionsLockExtension, VersionCatalogsExtension, BasePluginExtension, DefaultArtifactPublicationSet, ArtifactoryPluginConvention, PublishingExtension, GradleLintExtension, ReportingExtension, NodeExtension, PackageJsonExtension]

explicitly adding the java plugin in various spots didn't seem to do any good.