instrumentation-quickstart example log4j2 config always sends `logging.googleapis.com/trace_sampled: true`

[aabmass]

We send true even if trace was not sampled. See https://github.com/apache/logging-log4j2/discussions/2482 for context. In the meantime, sending true keeps the "View trace details" button working. Added in https://github.com/GoogleCloudPlatform/opentelemetry-operations-java/pull/330