EiffelConfig: fix invalid log format

Solves: Jira GER-1734
Change-Id: I3f2321d3ef197d546dfd3f2a23e34f8e8a25d059

src/main/java/com/googlesource/gerrit/plugins/eventseiffel/config/EiffelConfig.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/eventseiffel/config/EiffelConfig.java b/src/main/java/com/googlesource/gerrit/plugins/eventseiffel/config/EiffelConfig.java
index e04401a..7d43311 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/eventseiffel/config/EiffelConfig.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/eventseiffel/config/EiffelConfig.java
@@ -51,7 +51,7 @@
       logger.atInfo().log("namespace is not set in the config");
     } else {
       this.namespace = Optional.of(namespace);
-      logger.atInfo().log("namespace is set to: %d", namespace);
+      logger.atInfo().log("namespace is set to: %s", namespace);
     }
   }