Update non-thinking chat template

Removes `<|channel>thought\n<channel|>` from the non-thinking chat template.

The evals in the original checkpoint look better, please see https://huggingface.co/google/diffusiongemma-26B-A4B-it/discussions/15 (@joaogante ).

chat_template.jinja

@@ -356,8 +356,5 @@
 {%- if add_generation_prompt -%}
     {%- if ns.prev_message_type != 'tool_response' and ns.prev_message_type != 'tool_call' -%}
         {{- '<|turn>model\n' -}}
-        {%- if not enable_thinking | default(false) -%}
-            {{- '<|channel>thought\n<channel|>' -}}
-        {%- endif -%}
     {%- endif -%}
 {%- endif -%}