Auto merge of #95299 - mkroening:rm-hermitkernel, r=joshtriplett

Remove hermitkernel targets

RustyHermit now maintains custom json targets, which are distributed with the kernel: https://github.com/hermitcore/libhermit-rs/pull/395

See https://github.com/hermitcore/rusty-hermit/issues/197#issuecomment-1076667961
CC: `@stlankes,` `@bstrie`