chore: update to splunk-otel-js 2.4.0

From the changelog:

Fix the error message about an unavailable exporter (e.g. Exporter "otlp" requested through environment variable is unavailable.) when OTEL_TRACES_EXPORTER is set. Workaround for https://github.com/open-telemetry/opentelemetry-js/issues/3422. splunk-otel-lambda always set OTEL_TRACES_EXPORTER, so the users always saw this error even though nothing went wrong. https://github.com/signalfx/splunk-otel-js/pull/783
Fix for AWS Lambda instrumentation and a few others where they were logging unnecessary errors when MeterProvider wasn't set: https://github.com/open-telemetry/opentelemetry-js-contrib/blob/main/plugins/node/opentelemetry-instrumentation-aws-lambda/src/instrumentation.ts#L348-L354 Explicitly set a meter provider for instrumentations. NoopMeterProvider is set by default. If metrics are enabled and SPLUNK_INSTRUMENTATION_METRICS_ENABLED is set to true, instrumentation specific metrics will be emitted, for example http.server.duration from the http instrumentation. https://github.com/signalfx/splunk-otel-js/pull/784

signalfx / splunk-otel-lambda