default to grpc on kyma

[sjvans]

on kyma with cls and kind telemetry-to-otlp, we have get this env (exerpt):

  - name: OTEL_EXPORTER_OTLP_TRACES_ENDPOINT
    value: http://telemetry-otlp-traces.kyma-system.svc.cluster.local:4317/
  - name: OTEL_EXPORTER_OTLP_METRICS_ENDPOINT
    value: http://telemetry-otlp-metrics.kyma-system.svc.cluster.local:4317/

→ protocol isn't defined

however, the default protocol for js is http/protobuf (cf. here)

→ unsupported media type errors, as described in #259

works as designed, because telemetry-to-otlp relies on otlp config via env vars. however, bad dx.

• "workaround": set env var OTEL_EXPORTER_OTLP_PROTOCOL=grpc
• "solution" (this issue): if no env var re protocol is set (general and signal-specific!) but the endpoint config specifies port 4317, set signal-specific protocol config to grpc