oops, upate pacemaker visibility

Change-Id: I326e1a485c559f3e9d108d373deac5ea73913f62

Author: igorbernstein2

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/internal/csm/tracers/Pacemaker.java

@@ -33,7 +33,7 @@ public class Pacemaker implements Runnable {
 
   private Instant prev;
 
-  Pacemaker(RecorderRegistry registry, ClientInfo clientInfo, String name) {
+  public Pacemaker(RecorderRegistry registry, ClientInfo clientInfo, String name) {
     this.prev = Instant.now();
     this.registry = registry;
     this.clientInfo = clientInfo;