Opentelemetry-js: Invalid method used for initialising GlobalTracer in opentracing-shim example

[sleighzy]

The OpenTelemetry API was changed to use setGlobalTracerProvider(provider) instead of initGlobalTracerProvider(provider). The change made at the time appears to have broken the opentracing-shim example in the below two files as it also updated the opentracing.initGlobalTracer(shim) call to opentracing.setGlobalTracer(shim).

https://github.com/open-telemetry/opentelemetry-js/pull/839/files#diff-90edab116f366300c10d75d1152a0c90

https://github.com/open-telemetry/opentelemetry-js/pull/839/files#diff-91dfa22f1a98990b3bc83ba65bcdee0a

[sleighzy]

I'll have a PR for this shortly.