update descriptions

Author: zeitlinger

instrumentation-api-incubator/src/main/java/io/opentelemetry/instrumentation/api/incubator/semconv/rpc/RpcClientMetrics.java

@@ -63,7 +63,7 @@ private RpcClientMetrics(Meter meter) {
       DoubleHistogramBuilder stableDurationBuilder =
           meter
               .histogramBuilder("rpc.client.call.duration")
-              .setDescription("The duration of an outbound RPC invocation.")
+              .setDescription("Measures the duration of outbound remote procedure calls (RPC).")
               .setUnit("s");
       RpcMetricsAdvice.applyClientDurationAdvice(stableDurationBuilder, true);
       stableClientDurationHistogram = stableDurationBuilder.build();

instrumentation-api-incubator/src/main/java/io/opentelemetry/instrumentation/api/incubator/semconv/rpc/RpcServerMetrics.java

@@ -63,7 +63,7 @@ private RpcServerMetrics(Meter meter) {
       DoubleHistogramBuilder stableDurationBuilder =
           meter
               .histogramBuilder("rpc.server.call.duration")
-              .setDescription("The duration of an inbound RPC invocation.")
+              .setDescription("Measures the duration of inbound remote procedure calls (RPC).")
               .setUnit("s");
       RpcMetricsAdvice.applyServerDurationAdvice(stableDurationBuilder, true);
       stableServerDurationHistogram = stableDurationBuilder.build();