fix stablelm.py tensor-parallel-size bug (vllm-project#2482)

vllm/model_executor/models/stablelm.py

@@ -99,7 +99,7 @@ def __init__(self,
         self.q_size = self.num_heads * self.head_dim
         self.kv_size = self.num_key_value_heads * self.head_dim
 
-        if (self.head_dim * self.num_heads) != self.hidden_size:
+        if (self.head_dim * self.num_heads * tp_size) != self.hidden_size:
             raise ValueError(
                 f"hidden_size must be divisible by num_heads (got `hidden_size`: {self.hidden_size}"
                 f" and `num_heads`: {self.num_heads}).")