chore(ci): fix skipping test if chat completion not available [backport #7838 to 2.3] (#7842)

Backports #7838 to 2.3

#7759 introduced a regression test for testing openai's ChatCompletion
endpoint, but omitted a conditional test skip if the version of openai
being tested does not support ChatCompletions (`<=0.26.5`). For some
reason this was not being reported in regular CI runs but was being
caught on CI runs on the main branch.

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
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- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
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[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist

- [x] Title is accurate.
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[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
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Author: Yun-Kim

tests/contrib/openai/test_openai_v0.py

@@ -526,6 +526,8 @@ def test_chat_completion_tool_calling(openai, openai_vcr, snapshot_tracer):
     ],
 )
 def test_chat_completion_image_input(openai, openai_vcr, snapshot_tracer):
+    if not hasattr(openai, "ChatCompletion"):
+        pytest.skip("ChatCompletion not supported for this version of openai")
     image_url = (
         "https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Gfp-wisconsin-madison-the-nature-boardwalk"
         ".jpg/2560px-Gfp-wisconsin-madison-the-nature-boardwalk.jpg"