Remove PublicForTesting from Status.CanonicalCode.toStatus() (fixes #976).
Remove PublicForTesting from Status.CanonicalCode.toStatus() (fixes #976).

This method is already used by the Stackdriver stats exporter to convert status
types, so it should be part of the API.

bogdandrutu/opencensus-java,songy23/instrumentation-java,sebright/instrumentation-java,census-instrumentation/opencensus-java,sebright/opencensus-java,sebright/opencensus-java,bogdandrutu/opencensus-java,sebright/instrumentation-java,bogdandrutu/instrumentation-java,bogdandrutu/opencensus-java,census-instrumentation/opencensus-java,songy23/instrumentation-java,songy23/instrumentation-java,bogdandrutu/instrumentation-java,census-instrumentation/opencensus-java,sebright/opencensus-java