ReviewersResolver: Don't log stack trace when group does not exist

If the reviewer with name "foo" is in the config, but that user has
been deactivated, we then attempt to resolve "foo" as a group. When
the group also does not exist, a log is emitted.

Including the entire stack trace causes too much log spam.

Change-Id: I1c23373d64204a2accba141c775d218fe35aaa99
diff --git a/src/main/java/com/googlesource/gerrit/plugins/reviewers/ReviewersResolver.java b/src/main/java/com/googlesource/gerrit/plugins/reviewers/ReviewersResolver.java
index 95c8316..a1f9d9a 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/reviewers/ReviewersResolver.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/reviewers/ReviewersResolver.java
@@ -160,8 +160,7 @@
           "For the change {} of project {}: reviewer {} is neither an account nor a group.",
           changeNumber,
           project,
-          group,
-          e);
+          group);
     } catch (NoSuchProjectException | IOException | OrmException e) {
       log.warn(
           "For the change {} of project {}: failed to list accounts for group {}.",