Configuration cache compatibility

Plugin version 0.14 [became incompatible](https://builds.gradle.org/buildConfiguration/Gradle_Release_Check_ConfigCacheSmokeTestsJava8/68373818?hideProblemsFromDependencies=false&hideTestsFromDependencies=false&expandBuildProblemsSection=true&expandBuildChangesSection=true&expandBuildTestsSection=true) with the configuration cache.
```
FAILURE: Build failed with an exception.

* What went wrong:
Configuration cache problems found in this build.

1 problem was found storing the configuration cache.
- Task `:compilePlayRoutes` of type `org.gradle.playframework.tasks.RoutesCompile`: invocation of 'Task.project' at execution time is unsupported.
See https://docs.gradle.org/8.3-20230710200000+0000/userguide/configuration_cache.html#config_cache:requirements:use_project_during_execution

See the complete report at file:///Users/ov7a/work/gradle_copy/subprojects/smoke-test/build/tmp/te%C5%9Dt%20files/PlayExterna.Test/bbyb/build/reports/configuration-cache/ceytd1kss4ltxedelko6wj4po/4le2nn5j2bwz0jgy3sia0k46i/configuration-cache-report.html
> Invocation of 'Task.project' by task ':compilePlayRoutes' at execution time is unsupported.
```
0.13 works fine.

This can be reproduced with Gradle's [smoke tests](https://github.com/gradle/gradle/blob/b3a77d57d8a2d13d97b2b16a12f65f5fdee7fa1e/subprojects/smoke-test/src/smokeTest/groovy/org/gradle/smoketests/AbstractSmokeTest.groovy#L118)

Most probably the problem was introduced with [this line](https://github.com/gradle/playframework/blame/818d998bcca6bce1d2e8d7deaaecaf7a19be55a1/src/main/java/org/gradle/playframework/tasks/RoutesCompile.java#L106)