Add warning about spurious 'git cl upload' messages (#4800)

Fixes #4186

utils/roll_deps.sh

diff --git a/utils/roll_deps.sh b/utils/roll_deps.sh
index cef8b52..20c061f 100755
--- a/utils/roll_deps.sh
+++ b/utils/roll_deps.sh
@@ -39,6 +39,8 @@
     exit 1
 fi
 
+echo "*** Ignore messages about running 'git cl upload' ***"
+
 old_head=$(git rev-parse HEAD)
 
 set +e