Mk/bsd.default-versions.mk: update JAVA_DEFAULT to 25

The ports tree is adjusted and tested to be ready to set the default
java version to 25.

Openjdk 25 upstream dropped support for i386 so the default for i386
stays at openjdk21.

Thanks to everybody involved in making Java a vivid environment on
FreeBSD.

PR: 293559
Relnotes: yes