[Misc][MacOS] fix bfloat16 error (#18249)

Signed-off-by: reidliu41 <reid201711@gmail.com>
Co-authored-by: reidliu41 <reid201711@gmail.com>

Author: reidliu41

vllm/platforms/cpu.py

@@ -36,7 +36,7 @@ def supported_dtypes(self) -> list:
             # instead of checking the OS. For instance M2 shall supports bf16
             # already. But we need to modify `cpu_extension.cmake` to activate
             # the feature in the build.
-            return [torch.bfloat16, torch.float32]
+            return [torch.float16, torch.float32]
         # x86/aarch64 CPU has supported both bf16 and fp16 natively.
         return [torch.bfloat16, torch.float16, torch.float32]