cleanup imports in examples (#2300)

Author: r0fls

examples/metrics-basic/src/main.rs

@@ -1,5 +1,4 @@
-use opentelemetry::global;
-use opentelemetry::KeyValue;
+use opentelemetry::{global, KeyValue};
 use opentelemetry_sdk::metrics::{PeriodicReader, SdkMeterProvider};
 use opentelemetry_sdk::{runtime, Resource};
 use std::error::Error;