fix incorrect increase of hit count (#8533)

Co-authored-by: Zhiqiang Xie <xiezhq@stanford.edu>

python/sglang/srt/mem_cache/hiradix_cache.py

@@ -560,13 +560,11 @@ class HiRadixCache(RadixCache):
             prefix_len = self.key_match_fn(child.key, key)
             if prefix_len < len(child.key):
                 new_node = self._split_node(child.key, child, prefix_len)
-                self.inc_hit_count(new_node)
                 if not new_node.evicted:
                     value.append(new_node.value)
                 node = new_node
                 break
             else:
-                self.inc_hit_count(child)
                 if not child.evicted:
                     value.append(child.value)
                 node = child