[gomod] Bump go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc from 1.17.0 to 1.18.0 in /backend

[gomod] Bump go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc from 1.17.0 to 1.18.0 in /backend #643