Docs: Fix broken line breaks in snippets (#11523)

**Description:**
This PR fix some code snippets that have raw `\n`'s instead of actual
line breaks.

**Issue:**
Currently some snippets look like this:

![image](https://github.com/langchain-ai/langchain/assets/18213435/355b4911-38e9-4ba4-8570-f928557b6c13)

Affected pages:
-
https://python.langchain.com/docs/integrations/providers/predictionguard#example-usage
-
https://python.langchain.com/docs/modules/agents/how_to/custom_llm_agent#set-up-environment
-
https://python.langchain.com/docs/modules/chains/foundational/llm_chain#get-started
-
https://python.langchain.com/docs/integrations/providers/shaleprotocol#how-to

**Tag maintainer:**
@hwchase17

docs/docs_skeleton/docs/integrations/providers/predictionguard.mdx

@@ -37,7 +37,8 @@ import os
 
 import predictionguard as pg
 from langchain.llms import PredictionGuard
-from langchain.prompts import PromptTemplate\nfrom langchain.chains import LLMChain
+from langchain.prompts import PromptTemplate
+from langchain.chains import LLMChain
 
 # Your Prediction Guard API key. Get one at predictionguard.com
 os.environ["PREDICTIONGUARD_TOKEN"] = "<your Prediction Guard access token>"
@@ -76,7 +77,8 @@ Basic LLM Chaining with the Prediction Guard wrapper:
 ```python
 import os
 
-from langchain.prompts import PromptTemplate\nfrom langchain.chains import LLMChain
+from langchain.prompts import PromptTemplate
+from langchain.chains import LLMChain
 from langchain.llms import PredictionGuard
 
 # Optional, add your OpenAI API Key. This is optional, as Prediction Guard allows

docs/docs_skeleton/docs/integrations/providers/shaleprotocol.md

@@ -20,7 +20,8 @@ As of June 2023, the API supports Vicuna-13B by default. We are going to support
 For example
 ```python
 from langchain.llms import OpenAI
-from langchain.prompts import PromptTemplate\nfrom langchain.chains import LLMChain
+from langchain.prompts import PromptTemplate
+from langchain.chains import LLMChain
 
 import os
 os.environ['OPENAI_API_BASE'] = "https://shale.live/v1"

docs/snippets/modules/agents/how_to/custom_llm_agent.mdx

@@ -20,7 +20,9 @@ Do necessary imports, etc.
 ```python
 from langchain.agents import Tool, AgentExecutor, LLMSingleActionAgent, AgentOutputParser
 from langchain.prompts import StringPromptTemplate
-from langchain.llms import OpenAI\nfrom langchain.utilities import SerpAPIWrapper\nfrom langchain.chains import LLMChain
+from langchain.llms import OpenAI
+from langchain.utilities import SerpAPIWrapper
+from langchain.chains import LLMChain
 from typing import List, Union
 from langchain.schema import AgentAction, AgentFinish, OutputParserException
 import re

docs/snippets/modules/chains/foundational/llm_chain.mdx

@@ -1,5 +1,7 @@
 ```python
-from langchain.prompts import PromptTemplate\nfrom langchain.llms import OpenAI\nfrom langchain.chains import LLMChain
+from langchain.prompts import PromptTemplate
+from langchain.llms import OpenAI
+from langchain.chains import LLMChain
 
 prompt_template = "What is a good name for a company that makes {product}?"