Update model token mappings/cost to include 0613 models (#6122)

Add `gpt-3.5-turbo-16k` to model token mappings, as per the following
new OpenAI blog post:
https://openai.com/blog/function-calling-and-other-api-updates

Fixes #6118 


Co-authored-by: Harrison Chase <hw.chase.17@gmail.com>
Co-authored-by: Dev 2049 <dev.dev2049@gmail.com>

langchain/llms/openai.py

@@ -517,10 +517,15 @@ class BaseOpenAI(BaseLLM):
         model_token_mapping = {
             "gpt-4": 8192,
             "gpt-4-0314": 8192,
+            "gpt-4-0613": 8192,
             "gpt-4-32k": 32768,
             "gpt-4-32k-0314": 32768,
+            "gpt-4-32k-0613": 32768,
             "gpt-3.5-turbo": 4096,
             "gpt-3.5-turbo-0301": 4096,
+            "gpt-3.5-turbo-0613": 4096,
+            "gpt-3.5-turbo-16k": 16385,
+            "gpt-3.5-turbo-16k-0613": 16385,
             "text-ada-001": 2049,
             "ada": 2049,
             "text-babbage-001": 2040,