[Bug] Reenable OTLP export tests

[mjameswh]

Describe the bug

• Two of our TS integration tests for Core OTLP metrics exports have recently started being extremely noisy (warnings: OpenTelemetry metrics error occurred. Metrics exporter otlp failed with the grpc server returns error (Internal error): , detailed error message: Missing response message.). Those tests are using a bare HTTP2 server to grossly emulate a OTLP collector grpc-service. Due to a recent update to Core (maybe to one of its underlying dependencies), the OTLP emitter now reports failure to get a proper grpc response form the collector service.

• These error messages have coincided with one case where our integration tests completely hanged in CI (I stopped them after 3.5 hours), though I don't know at this point either there is an actual connection between the these two symptoms.

• Until we can rewrite those tests to use a more convincing mock collector, I have disabled those tests.