Set `add_bos_token` to `false` to prevent auto-adding `<|bos|>` in prompts from GGUF files

When converting to GGUF, if we have this set to `true`, it will automatically add a `<|bos|>` in front of the prompt, which negatively affects the generation. So I recommend setting it to `false` here.

PS: I've set it to `false` locally before converting [M4-ai/TinyMistral-248M-v2-Instruct-GGUF](https://huggingface.co/M4-ai/TinyMistral-248M-v2-Instruct-GGUF).

tokenizer_config.json

@@ -1,5 +1,5 @@
 {
-  "add_bos_token": true,
+  "add_bos_token": false,
   "add_eos_token": false,
   "added_tokens_decoder": {
     "0": {