doc: fix bug report Github template formatting (#17486)

Signed-off-by: David Xia <david@davidxia.com>

.github/ISSUE_TEMPLATE/400-bug-report.yml

@@ -21,7 +21,7 @@ body:
       It is suggested to download and execute the latest script, as vllm might frequently update the diagnosis information needed for accurately and quickly responding to issues.
     value: |
       <details>
-      <summary>The output of `python collect_env.py`</summary>
+      <summary>The output of <code>python collect_env.py</code></summary>
 
       ```text
       Your output of `python collect_env.py` here