Fix FloggerLogString issues flagged by error prone

See: [1] for more details.

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

Change-Id: I82c20d69c74b9ea8430a1cc5fdec5c99ca40534c

src/main/java/com/googlesource/gerrit/plugins/hooks/HookExecutor.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/hooks/HookExecutor.java b/src/main/java/com/googlesource/gerrit/plugins/hooks/HookExecutor.java
index 6f2fade..5b642d3 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/hooks/HookExecutor.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/hooks/HookExecutor.java
@@ -65,10 +65,10 @@
       return task.get(timeout, TimeUnit.SECONDS);
     } catch (TimeoutException e) {
       message = "Synchronous hook timed out " + hook;
-      logger.atSevere().log(message);
+      logger.atSevere().log("%s", message);
     } catch (Exception e) {
       message = "Error running hook " + hook;
-      logger.atSevere().withCause(e).log(message);
+      logger.atSevere().withCause(e).log("%s", message);
     }
     task.cancel(true);
     hookTask.cancel();