Remove db.redis.flags attribute implementation

[tiagodaraujo]

Component

OpenTelemetry.Instrumentation.StackExchangeRedis

Is your feature request related to a problem?

The db.redis.flags attribute is being written to the OpenTelemetry.Instrumentation.StackExchangeRedis traces but this field is not in the semantic conventions : https://github.com/open-telemetry/semantic-conventions/blob/main/docs/database/redis.md.

This field should be removed from the implementation.

What is the expected behavior?

The db.redis.flags attribute should not exist in traces and metrics

Which alternative solutions or features have you considered?

Add the attribute to the semantic conventions: https://github.com/open-telemetry/semantic-conventions/blob/main/docs/database/redis.md

Additional context

Also discussed here: #1982 (comment)