tracing documentation is wrong

[pmeier]

This is a follow-up to #190, which was marked as fixed by #203. However, the explanation in the docs does not work and to the best of my understanding cannot work.

As https://github.com/valkey-io/valkey-py/issues/190#issuecomment-2845363088 called out, the RedisInstrumentor instruments the redis.Redis class. And since valkey-py is a fork of redis-py rather than a wrapper, even if you install both, instrumenting redis-py has no effect on valkey-py.

Until open-telemetry/opentelemetry-python-contrib#3478 or similar is resolved, the documentation should state that tracing is not supported.