RefUpdateListener: Use Logger's built-in string formatting

Change-Id: I1457cfc3a558456f7f24335d5fae822487ec229d

src/main/java/com/googlesource/gerrit/plugins/refprotection/RefUpdateListener.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/refprotection/RefUpdateListener.java b/src/main/java/com/googlesource/gerrit/plugins/refprotection/RefUpdateListener.java
index 674e880..30e272f 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/refprotection/RefUpdateListener.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/refprotection/RefUpdateListener.java
@@ -135,9 +135,10 @@
     RefUpdateAttribute refUpdate = event.refUpdate.get();
     if (refUpdate.newRev.equals(ObjectId.zeroId().getName())) {
       log.info(
-          String.format(
-              "Ref Deleted: project [%s] refname [%s] old object id [%s]",
-              event.getProjectNameKey().toString(), event.getRefName(), refUpdate.oldRev));
+          "Ref Deleted: project [{}] refname [{}] old object id [{}]",
+          event.getProjectNameKey(),
+          event.getRefName(),
+          refUpdate.oldRev);
       return true;
     }
     return false;