instrumentation-genai: stop setting OTEL_PYTHON_LOGGING_AUTO_INSTRUMENTATION_ENABLED=true (#4263)

The openai-v2 examples predate (2024) the Jan 2025 decouple
(f3b9e6ec96b7cc3717d5c8b529da7a8923810973 in core) of the log machinery setup from
the LoggingHandler setup. So unless I'm missing something and you
really want to see OpenTelemetry logs shipped from Python logging module
usage in these genai examples I think we can drop these.

We're moving the logging handler from the sdk to the opentelemetry-instrumentation-logging and
deprecating that environment variable.