[llvm] [RISCV][llvm-exegesis] Simplify copying a SmallVector to a std::vector. NFC (PR #122988)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 approved this pull request.

LGTM.

Thanks for the cleanup.

https://github.com/llvm/llvm-project/pull/122988