core[patch]: Add clarification about streaming to RunnableLambda (#23227)

Add streaming clarification to runnable lambda docstring.

libs/core/langchain_core/runnables/base.py

@@ -3576,6 +3576,11 @@ class RunnableLambda(Runnable[Input, Output]):
     RunnableLambda can be composed as any other Runnable and provides
     seamless integration with LangChain tracing.
 
+    `RunnableLambda` is best suited for code that does not need to support
+    streaming. If you need to support streaming (i.e., be able to operate
+    on chunks of inputs and yield chunks of outputs), use `RunnableGenerator`
+    instead.
+
     Examples:
 
         .. code-block:: python