[build] Remove statically linked JNI artifacts

[Gold856]

The loading framework for the -jni artifacts was removed in #6600, so these just don't work anymore. We can remove them to reduce the amount of space used when building and save some time as well (although the gains seem to be marginal).

Reference for CI build times and space savings: https://github.com/Gold856/allwpilib/actions/runs/12348391056

[ThadHouse]

The gains are marginal because how we do the building, these projects basically cost just a linking step. iirc they don't even compile anything, or if they do its 1 or 2 files.

Otherwise, I generally think I'm ok with this. You're right they're broken. They've also been broken for years anyway.