Update open telemetry tracing code according to new spec.

[vi3k6i5]

The method used in open telemetry tracing has been updated in this commit

Environment details

opentelemetry-api 1.2.0
opentelemetry-sdk 1.2.0
google-cloud-spanner 3.4.0

Steps to reproduce

from opentelemetry.trace.status import Status, StatusCanonicalCode    

from opentelemetry.instrumentation.utils import http_status_to_canonical_code

Stack trace

ImportError: cannot import name 'StatusCanonicalCode' from 'opentelemetry.trace.status'

SO question link: https://stackoverflow.com/questions/67775140/getting-import-error-while-trying-to-import-statuscanonicalcode-using-openteleme