Tracing Tests E2E NON-GLOBAL-OTEL GRPC: document reference set() failed

Note: #8379 was also for this test, but it was closed more than 10 days ago. So, I didn't mark it flaky. ---- commit: ecf348bed2cc5678d78e4950f6aa417e73ab26b4 buildURL: [Build Status](https://source.cloud.google.com/results/invocations/ecabdaec-7968-4b85-a038-979602682c09), [Sponge](http://sponge2/ecabdaec-7968-4b85-a038-979602682c09) status: failed