IndexEventHandler: Fix FloggerFormatString warning

Build is failing with recent Error Prone version:

  IndexEventHandler.java:119: error: [FloggerFormatString]
  extra format arguments: used 0, provided 1
        log.atWarning().withCause(e).log("Unable to create task to reindex change {}", changeId);
                                        ^
    (see https://errorprone.info/bugpattern/FloggerFormatString)

Change-Id: If27fa57b4e5ab08a0fabb5f1cc0f1c6468bb050e

src/main/java/com/ericsson/gerrit/plugins/highavailability/index/IndexEventHandler.java

diff --git a/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/IndexEventHandler.java b/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/IndexEventHandler.java
index 73e842f..4f77508 100644
--- a/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/IndexEventHandler.java
+++ b/src/main/java/com/ericsson/gerrit/plugins/highavailability/index/IndexEventHandler.java
@@ -116,7 +116,7 @@
                   }
                 });
       } catch (Exception e) {
-        log.atWarning().withCause(e).log("Unable to create task to reindex change {}", changeId);
+        log.atWarning().withCause(e).log("Unable to create task to reindex change %s", changeId);
       }
     }
   }