once open-telemetry/opentelemetry-specification#4536 is merged and released in the spec.

The "spec_unstable_logs_enabled" feature flag needs to be removed completely. All methods/code should be enabled always.
Do this for opentelemetry, opentelemetry_sdk, opentelemetry-appender-tracing and opentelemetry-appender-log crates.
Also update changelog.md file for all above crates to inform of the above change.

Once done, do a thorough search across repo to find any "spec_unstable_logs_enabled" references, and remove them. If there are places where it cannot be removed, create issues to track as follow ups.