Self-hosted runners may not be working

[ninovanhooff]

I forked this template to a private repo and changed the runners to the self-hosted ones.

The build failed with:

Run ./gradlew assembleDevDebug --stacktrace

Welcome to Gradle 8.7!

Here are the highlights of this release:
 - Compiling and testing with Java 22
 - Cacheable Groovy script compilation
 - New methods in lazy collection properties

 Caused by: java.lang.IllegalArgumentException: Unsupported class file major version 66

Note that the runner uses java 21 and gradle uses java 22

[ninovanhooff]

Note some discuission with documentation here: https://github.com/Q42/Template.Android/pull/78#discussion_r1755093403