[clang] [clang-repl] Suppress [[nodiscard]] warnings for REPL printed express (PR #178661)

[Yanzuo Liu via cfe-commits]

zwuis wrote:

You have _one week_ in between pings: https://llvm.org/docs/CodeReview.html#code-reviews-speed-and-reciprocity

https://github.com/llvm/llvm-project/pull/178661