Apply suggestions from code review

Author: martincostello

README.md

@@ -60,7 +60,7 @@ SDKs](https://grafana.com/docs/grafana-cloud/send-data/otlp/send-data-otlp/#push
 ```sh
 export OTEL_EXPORTER_OTLP_PROTOCOL="http/protobuf"
 export OTEL_EXPORTER_OTLP_ENDPOINT="https://otlp-gateway-prod-eu-west-0.grafana.net/otlp"
-export OTEL_EXPORTER_OTLP_HEADERS="Authorization=Basic a-secret-token"
+export OTEL_EXPORTER_OTLP_HEADERS="Authorization=Basic base64-encoded-string"
 ```
 
 > [!TIP]