Reduce spamming by lowering to debug the invalid changes

When a repository contains invalid change refs, the notification
would help only the Gerrit admin interested in that information
and does not make sense to trace as warning the same warning
over and over again.

Change-Id: I2d7c62aeb1e827c2f3346d004737dc172caa290c
diff --git a/src/main/java/com/googlesource/gerrit/modules/gitrefsfilter/ForProjectWrapper.java b/src/main/java/com/googlesource/gerrit/modules/gitrefsfilter/ForProjectWrapper.java
index 3080694..23c26ac 100644
--- a/src/main/java/com/googlesource/gerrit/modules/gitrefsfilter/ForProjectWrapper.java
+++ b/src/main/java/com/googlesource/gerrit/modules/gitrefsfilter/ForProjectWrapper.java
@@ -121,7 +121,7 @@
           changeNotesFactory.createChecked(repo, project, changeId, changeRevision);
       return changeNotes.getChange().getStatus().isOpen();
     } catch (NoSuchChangeException e) {
-      logger.atWarning().withCause(e).log(
+      logger.atFine().withCause(e).log(
           "Change %d does not exist: hiding from the advertised refs", changeId);
       return false;
     }