[llvm] [RISCV] Remove setJumpIsExpensive(). (PR #74647)

[Philip Reames via llvm-commits]

https://github.com/preames approved this pull request.

LGTM - I suspect we're going to want a more fine grained decision here, but I'm fine flipping the default in the meantime.  

https://github.com/llvm/llvm-project/pull/74647