[CI] Disable flaky structured output test from CI (vllm-project#24366)

Signed-off-by: Roger Wang <hey@rogerw.io>

Author: ywang96

tests/v1/entrypoints/llm/test_struct_output_generate.py

@@ -41,8 +41,9 @@
 PARAMS_MODELS_BACKENDS_TOKENIZER_MODE = [
     ("mistralai/Ministral-8B-Instruct-2410", "xgrammar", "auto", None),
     ("mistralai/Ministral-8B-Instruct-2410", "guidance", "auto", None),
-    ("mistralai/Ministral-8B-Instruct-2410", "lm-format-enforcer", "auto",
-     None),
+    #FIXME: This test is flaky on CI thus disabled
+    #("mistralai/Ministral-8B-Instruct-2410", "lm-format-enforcer", "auto",
+    # None),
     ("mistralai/Ministral-8B-Instruct-2410", "xgrammar", "mistral", None),
     ("Qwen/Qwen2.5-1.5B-Instruct", "xgrammar", "auto", None),
     ("Qwen/Qwen2.5-1.5B-Instruct", "lm-format-enforcer", "auto", None),