[clang] [clang] fix half && bfloat16 convert node expr codegen (PR #89051)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

Looks like automation didn't trigger, but:

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(I'll also wait a bit to give @arsenm a chance to respond.)

https://github.com/llvm/llvm-project/pull/89051