Refresh the Zipkin observability tutorial

## Describe the feature

The [observability tutorial](https://github.com/dapr/quickstarts/tree/master/tutorials/observability) is dated and should be updated with the following:
- Dapr does not use OpenCensus at all, this sentence can be deleted.
- Add a better introduction that mentions Dapr works with both Zipkin and OLTP protocols
- Add a note that mentions Zipkin is great for development but not typically recommended in production scenarios
- Check all the links and run through the tutorial to ensure it works with the latest version of Dapr (1.12)