[Bugfix][CI/Build] Fix failing Mteb CI (#26638)

Signed-off-by: Isotr0py <mozf@mail2.sysu.edu.cn>

vllm/model_executor/layers/layernorm.py

@@ -318,7 +318,11 @@ class GemmaRMSNorm(CustomOp):
         """PyTorch-native implementation equivalent to forward()."""
         orig_dtype = x.dtype
         if residual is not None:
-            x = x + residual.float() if orig_dtype == torch.float16 else x + residual
+            x = (
+                x.float() + residual.float()
+                if orig_dtype == torch.float16
+                else x + residual
+            )
             residual = x
 
         x = x.float()