Update Mosaic endpoint input/output api (#7391)

As noted in prior PRs (https://github.com/hwchase17/langchain/pull/6060,
https://github.com/hwchase17/langchain/pull/7348), the input/output
format has changed a few times as we've stabilized our inference API.
This PR updates the API to the latest stable version as indicated in our
docs: https://docs.mosaicml.com/en/latest/inference.html

The input format looks like this:

`{"inputs": [<prompt>]}
`

The output format looks like this:
`
{"outputs": [<output_text>]}
`
---------

Co-authored-by: Bagatur <baskaryan@gmail.com>

docs/extras/integrations/llms/mosaicml.ipynb

@@ -63,7 +63,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "llm = MosaicML(inject_instruction_format=True, model_kwargs={\"do_sample\": False})"
+    "llm = MosaicML(inject_instruction_format=True, model_kwargs={\"max_new_tokens\": 128})"
    ]
   },
   {