Replace tracing sample that using OpenCensus with the sample that using OpenTelemetry

[minherz]

The OpenCensus project is discontinued in favor of OpenTelemetry. As a part of the migration to OpenTelemetry the tracing sample should be taken down and replace with the code sample that uses OpenTelemetry.

The current code sample should be removed.

Creating another sample or cloning the existing one into this repository would generate duplication of maintenance efforts. The public documentation that references this sample is featured to removal and the existing tracing sample for OT is already referencing the OT sample.