fix: update pad token in special tokens following upstream

special_tokens_map.json

@@ -1,5 +1,5 @@
 {
   "bos_token": "<|begin_of_text|>",
   "eos_token": "<|end_of_text|>",
-  "pad_token": "<|finetune_right_pad_id|>"
+  "pad_token": "<|finetune_right_pad|>"
 }