Update example.go documentation (#1013)

ProbabilitySampler was renamed to TraceIDRatioBased

Signed-off-by: Pranav Sharma <sharmapranav@google.com>

Author: psx95

example/trace/otlpgrpc/example.go

@@ -52,7 +52,7 @@ func initTracer() (func(), error) {
 
 	tp := sdktrace.NewTracerProvider(
 		// For this example code we use sdktrace.AlwaysSample sampler to sample all traces.
-		// In a production application, use sdktrace.ProbabilitySampler with a desired probability.
+		// In a production application, use sdktrace.TraceIDRatioBased with a desired probability.
 		sdktrace.WithSampler(sdktrace.AlwaysSample()),
 		sdktrace.WithBatcher(exporter))