ci: mark unreliable langchain_community tests (#9490)

This change marks some unreliable tests in the langchain_community
suite. Some of these had been recently unmarked in
ecc56cf,
but it seems like they still have some underlying unreliability
([example](https://app.circleci.com/pipelines/github/DataDog/dd-trace-py/63192/workflows/693a2566-c19c-43c9-9f62-fda445a51e29/jobs/3926490)).

## Checklist

- [x] Change(s) are motivated and described in the PR description
- [x] Testing strategy is described if automated tests are not included
in the PR
- [x] Risks are described (performance impact, potential for breakage,
maintainability)
- [x] Change is maintainable (easy to change, telemetry, documentation)
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed or label `changelog/no-changelog` is set
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/))
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))
- [x] If this PR changes the public interface, I've notified
`@DataDog/apm-tees`.

## Reviewer Checklist

- [x] Title is accurate
- [x] All changes are related to the pull request's stated goal
- [x] Description motivates each change
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- [x] Testing strategy adequately addresses listed risks
- [x] Change is maintainable (easy to change, telemetry, documentation)
- [x] Release note makes sense to a user of the library
- [x] Author has acknowledged and discussed the performance implications
of this PR as reported in the benchmarks PR comment
- [x] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Author: emmettbutler

tests/contrib/langchain/test_langchain_community.py

@@ -243,6 +243,7 @@ def test_openai_chat_model_sync_generate(langchain, langchain_openai, request_vc
         )
 
 
+@flaky(1735812000)
 @pytest.mark.snapshot
 def test_openai_chat_model_vision_generate(langchain_openai, request_vcr):
     """
@@ -473,6 +474,7 @@ def test_embedding_logs(langchain_openai, ddtrace_config_langchain, request_vcr,
     mock_metrics.count.assert_not_called()
 
 
+@flaky(1735812000)
 @pytest.mark.snapshot
 def test_openai_math_chain_sync(langchain, langchain_openai, request_vcr):
     """
@@ -484,6 +486,7 @@ def test_openai_math_chain_sync(langchain, langchain_openai, request_vcr):
         chain.invoke("what is two raised to the fifty-fourth power?")
 
 
+@flaky(1735812000)
 @pytest.mark.snapshot(token="tests.contrib.langchain.test_langchain_community.test_chain_invoke")
 def test_chain_invoke_dict_input(langchain, langchain_openai, request_vcr):
     prompt_template = "what is {base} raised to the fifty-fourth power?"
@@ -580,6 +583,7 @@ def _transform_func(inputs):
         sequential_chain.invoke({"text": input_text, "style": "a 90s rapper"})
 
 
+@flaky(1735812000)
 @pytest.mark.snapshot
 def test_openai_sequential_chain_with_multiple_llm_sync(langchain, langchain_openai, request_vcr):
     template = """Paraphrase this text:
@@ -659,6 +663,7 @@ async def test_openai_sequential_chain_with_multiple_llm_async(langchain, langch
         await sequential_chain.ainvoke({"input_text": input_text})
 
 
+@flaky(1735812000)
 @pytest.mark.parametrize(
     "ddtrace_config_langchain",
     [dict(metrics_enabled=False, logs_enabled=True, log_prompt_completion_sample_rate=1.0)],
@@ -1112,6 +1117,7 @@ def test_lcel_chain_simple(langchain_core, langchain_openai, request_vcr):
         chain.invoke({"input": "how can langsmith help with testing?"})
 
 
+@flaky(1735812000)
 @pytest.mark.snapshot
 def test_lcel_chain_complicated(langchain_core, langchain_openai, request_vcr):
     prompt = langchain_core.prompts.ChatPromptTemplate.from_template(