Fix import when trace is missing from opentelemetry

[nicoloboschi]

otel dependency is optional but if I try to use latest elastic client it fails to bootstrap due to

../../../vdp/config_verification/elastic_sink/elastic_config_verification.py:21: in <module>
    from elasticsearch import Elasticsearch
../../../../.venv/lib/python3.11/site-packages/elasticsearch/__init__.py:45: in <module>
    from ._async.client import AsyncElasticsearch as AsyncElasticsearch
../../../../.venv/lib/python3.11/site-packages/elasticsearch/_async/client/__init__.py:38: in <module>
    from ._base import (
../../../../.venv/lib/python3.11/site-packages/elasticsearch/_async/client/_base.py:48: in <module>
    from ..._otel import OpenTelemetry
../../../../.venv/lib/python3.11/site-packages/elasticsearch/_otel.py:25: in <module>
    from opentelemetry import trace
E   ImportError: cannot import name 'trace' from 'opentelemetry' (unknown location)

Fix

While is usually correct to catch ModuleNotFoundError, in case of opentelemetry this is a bit different since the actual "opentelemetry" package doesn't exist at all (we got opentelemetry-api and opentelemetry-sdk) and in that case Python (3.11 in my case) throws a more generic ImportError

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[pquentin]

buildkite test this please

[pquentin]

Thank you for your contribution, it is now released as part of 8.16.0: https://github.com/elastic/elasticsearch-py/releases/tag/v8.16.0