Hotfix RetrievalQA Docs: docs: Fix formatting (#21183)

# Newline Characters breaking formatting 

**Description**: 
As you can see in the image below, the formatting in the documentation
is broken. As far as I can see the two added `\n` characters are
breaking the documentation. Therefore I would propose to remove those

![image](https://github.com/langchain-ai/langchain/assets/88305668/23b6e726-71b2-4812-91ea-3e8600683733)

**Dependencies**:
None

**Twitter Handle**
- epu9byj

---------

Co-authored-by: gere <gere@kapo.zh.ch>
Co-authored-by: Chester Curme <chester.curme@gmail.com>

libs/langchain/langchain/chains/retrieval_qa/base.py

@@ -216,8 +216,8 @@ class RetrievalQA(BaseRetrievalQA):
             system_prompt = (
                 "Use the given context to answer the question. "
                 "If you don't know the answer, say you don't know. "
-                "Use three sentence maximum and keep the answer concise."
-                "\n\n{context}"
+                "Use three sentence maximum and keep the answer concise. "
+                "Context: {context}"
             )
             prompt = ChatPromptTemplate.from_messages(
                 [