RefUpdateListener: Fix FloggerLogString issue flagged by error prone

See: [1] for more details.

[1] https://errorprone.info/bugpattern/FloggerLogString

Change-Id: I4944e1b9749e86eda2937eb760dfa752cf02ffe7

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

diff --git a/src/main/java/com/googlesource/gerrit/plugins/reviewnotes/RefUpdateListener.java b/src/main/java/com/googlesource/gerrit/plugins/reviewnotes/RefUpdateListener.java
index d18d1df..acc2ead 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/reviewnotes/RefUpdateListener.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/reviewnotes/RefUpdateListener.java
@@ -114,7 +114,7 @@
               })
           .call();
     } catch (RestApiException | UpdateException x) {
-      logger.atSevere().withCause(x).log(x.getMessage());
+      logger.atSevere().withCause(x).log("%s", x.getMessage());
     }
   }
 }