[Core][VLM] Test registration for OOT multimodal models (#8717)

Co-authored-by: DarkLight1337 <tlleungac@connect.ust.hk>

vllm/engine/llm_engine.py

@@ -290,9 +290,6 @@ class LLMEngine:
             model_config.mm_processor_kwargs,
         )
         # TODO(woosuk): Print more configs in debug mode.
-        from vllm.plugins import load_general_plugins
-        load_general_plugins()
-
         self.model_config = model_config
         self.cache_config = cache_config
         self.lora_config = lora_config