Prevent Lettuce Redis db.namespace being included in span names

[trask]

Summary

This makes Lettuce 5.1 library span-name extraction ignore db.namespace. Redis stable semantic conventions do not use the Redis database index (db.namespace) as a span-name target.

Today Lettuce 5.1 does not appear to expose the selected Redis database index to command spans through its upstream tracing API. This is defensive for if/when upstream Lettuce starts emitting db.namespace as a command span tag.

[Copilot]

Pull request overview

This PR adjusts Lettuce 5.1 span-name extraction to ensure Redis db.namespace (Redis database index) is not used as a span-name target, aligning with Redis stable semantic conventions and preventing future upstream tag changes from affecting span names.

Changes:

• Use a span-name-specific DbClientAttributesGetter for Lettuce 5.1 that always returns null for getDbNamespace() when computing span names.
• Make LettuceDbAttributesGetter non-final to allow the span-name-specific override.
• Add a clarifying comment in Jedis 4.0 singleton initialization to match the same Redis span-naming rationale.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
instrumentation/lettuce/lettuce-5.1/library/src/main/java/io/opentelemetry/instrumentation/lettuce/v5_1/LettuceTelemetryBuilder.java	Ensures Redis db.namespace is ignored for span-name extraction by using a specialized getter.
instrumentation/lettuce/lettuce-5.1/library/src/main/java/io/opentelemetry/instrumentation/lettuce/v5_1/LettuceDbAttributesGetter.java	Removes final to enable a span-name-only subclass override of getDbNamespace().
instrumentation/jedis/jedis-4.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/jedis/v4_0/JedisSingletons.java	Adds documentation comment explaining why db.namespace is masked for Redis span naming.