[Bug] Fix log issue with `\n` (#31390)

Signed-off-by: yewentao256 <zhyanwentao@126.com>
Signed-off-by: Wentao Ye <44945378+yewentao256@users.noreply.github.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: Robert Shaw <114415538+robertgshaw2-redhat@users.noreply.github.com>

vllm/v1/attention/backends/mla/flashmla_sparse.py

@@ -930,8 +930,8 @@ class FlashMLASparseImpl(MLACommonBaseImpl[FlashMLASparseMetadata]):
         if self.num_heads % self.padding != 0:
             assert self.padding % self.num_heads == 0
             logger.warning_once(
-                f"padding num_heads to {self.padding} \
-                    due to sparse attn kernel requirement"
+                f"padding num_heads to {self.padding} due to sparse attn "
+                "kernel requirement"
             )
             q_padded = q.new_empty((q.shape[0], self.padding, q.shape[2]))
             q_padded[:, : self.num_heads, :] = q