Fix examples and the link in experimental JSON file format (#2886)
Fix examples and the link in experimental JSON file format (#2886)

- The severityNumber field is an enum and must use a numeric value according this:
https://github.com/open-telemetry/opentelemetry-specification/pull/2758
- Link to a more appropriate section of otlp.md doc.
- Remove deprecatedCode
- Use numeric value for status code
open-telemetry/opentelemetry-specification,open-telemetry/opentelemetry-specification