fix otel docker file environment

Author: yagrxu

apps/dockerfiles/Dockerfile_03_otel

@@ -20,6 +20,7 @@ ENV OTEL_PROPAGATORS "tracecontext,baggage,xray"
 ENV OTEL_RESOURCE_ATTRIBUTES "service.name=unicorn-store-spring"
 ENV OTEL_IMR_EXPORT_INTERVAL "10000"
 ENV OTEL_EXPORTER_OTLP_ENDPOINT "http://localhost:4317"
+ENV OTEL_EXPORTER_OTLP_PROTOCOL "grpc"
 
 RUN groupadd --system spring -g 1000
 RUN adduser spring -u 1000 -g 1000