[Tools] change max_tokens default value to 512 (#1417)

This pull request includes a single change to the `openai_gpt4v.yaml`
file in the `promptflow-tools` package. The default value for
`max_tokens` has been updated to 512.

* <a
href="diffhunk://#diff-b9a4c02387f38efc06088f27b380851606f5e7b646aa65c3e6819d772a30f63dL35-R35">`src/promptflow-tools/promptflow/tools/yamls/openai_gpt4v.yaml`</a>:
Updated the default value for `max_tokens` to 512.# Description

Please add an informative description that covers that changes made by
the pull request and link all relevant issues.

# All Promptflow Contribution checklist:
- [ ] **The pull request does not introduce [breaking changes].**
- [ ] **CHANGELOG is updated for new features, bug fixes or other
significant changes.**
- [ ] **I have read the [contribution guidelines](../CONTRIBUTING.md).**
- [ ] **Create an issue and link to the pull request to get dedicated
review from promptflow team. Learn more: [suggested
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## General Guidelines and Best Practices
- [ ] Title of the pull request is clear and informative.
- [ ] There are a small number of commits, each of which have an
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appear in the history of the PR. For more information on cleaning up the
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### Testing Guidelines
- [ ] Pull request includes test coverage for the included changes.

---------

Co-authored-by: Meng Lan <[email protected]>

docs/reference/tools-reference/openai-gpt-4v-tool.md

@@ -29,7 +29,7 @@ Setup connections to provisioned resources in prompt flow.
 | connection             | OpenAI      | the OpenAI connection to be used in the tool                                                   | Yes      |
 | model                  | string      | the language model to use, currently only support gpt-4-vision-preview                         | Yes      |
 | prompt                 | string      | The text prompt that the language model will use to generate it's response.                    | Yes      |
-| max\_tokens            | integer     | the maximum number of tokens to generate in the response. Default is a low value decided by [OpenAI API](https://platform.openai.com/docs/guides/vision).                      | No       |
+| max\_tokens            | integer     | the maximum number of tokens to generate in the response. Default is 512.                      | No       |
 | temperature            | float       | the randomness of the generated text. Default is 1.                                            | No       |
 | stop                   | list        | the stopping sequence for the generated text. Default is null.                                 | No       |
 | top_p                  | float       | the probability of using the top choice from the generated tokens. Default is 1.               | No       |

src/promptflow-tools/promptflow/tools/yamls/openai_gpt4v.yaml

@@ -32,7 +32,7 @@ promptflow.tools.openai_gpt4v.OpenAI.chat:
       type:
         - double
     max_tokens:
-      default: ""
+      default: 512
       type:
         - int
     stop: