Upgrade to Groovy 2.5.10 (for JDK 14 compatibility) #24719
Description
Groovy 2.5.10 comes with basic JDK 14 support now, and it looks like we can use it as the sole version in our build: i.e. there is no need to differentiate between customJavaHome and regular execution with conditional use of Groovy 3.0.x anymore.
We'll upgrade to Groovy 3.0 proper for the Spring Framework 5.3 line.