refactor(resource-detector-gcp): migrate away from getEnv()

Author: pichlermarc

detectors/node/opentelemetry-resource-detector-gcp/src/detectors/GcpDetector.ts

@@ -79,7 +79,7 @@ class GcpDetector implements DetectorSync {
     attributes[SEMRESATTRS_CLOUD_AVAILABILITY_ZONE] = zoneId;
     attributes[SEMRESATTRS_CLOUD_PROVIDER] = CLOUDPROVIDERVALUES_GCP;
 
-    if (getEnv().KUBERNETES_SERVICE_HOST)
+    if (process.env.KUBERNETES_SERVICE_HOST)
       this._addK8sAttributes(attributes, clusterName);
 
     return attributes;