Avoid duplicate telemetry while using langchain instrumentation

As langchain and underlying library supporting telemetry can both emit telemetry producing duplicate data. One of the telemetry can be suppressed, please see discussion in the comments here:
https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3665#discussion_r2341713191
https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3665#issuecomment-3259366086