[gomod] Bump go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc from 0.42.0 to 0.43.0 in /backend

[gomod] Bump go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc from 0.42.0 to 0.43.0 in /backend #594