Release langchain-core==0.2.4

Changes since langchain-core==0.2.3

core[patch]: Release 0.2.4 (#22489)
core[patch]: bump langsmith (#22476)
Use immutable sequence type for batch/batch_as_completed types (#22433)
core[patch]: Fix VectorStore's as_retriever mutating tags param (#22470)
core(patch):fix partial_variables not working with SystemMessagePromptTemplate (#20711)
core[patch]: RFC: Allow concatenation of messages with multi part content (#22002)
core: In BaseRetriever make get_relevant_docs delegate to invoke (#22434)
core: In RunnableSequence pass kwargs to the first step (#22393)