OkHttpGrpcSender no longer logs retry attempts #8966

Describe the bug
OkHttpGrpcSender no longer logs retry attempts. #6614 added per-attempt FINER logs in RetryInterceptor; #8854 moved gRPC retries into OkHttpGrpcSender.sendAttempt() without them.

Steps to reproduce

1. Use the OTLP gRPC exporter with the default OkHttp sender (retry is on by default).
2. Set the JUL level of io.opentelemetry.exporter.sender.okhttp.internal to FINER.
3. Export to an endpoint with nothing listening.

What did you expect to see?
One Attempt N failed with retryable exception record per attempt, as the OkHttp HTTP sender (RetryInterceptor) and JdkHttpSender still log.

What did you see instead?
Only the final export failure. The Callback in OkHttpGrpcSender.sendAttempt() does not log.

What version and what artifacts are you using?
Artifacts: opentelemetry-exporter-sender-okhttp, opentelemetry-exporter-otlp
Version: 1.67.0 / main @ b32298a
How did you reference these artifacts? Gradle

Environment
Compiler: Temurin 21
OS: N/A

Additional context
N/A