build: fix bazel-stamp-vars

Don't output any strings other than the versions. This was messing up
the version being stamped in release npm packages to always be 0.0.0.

Author: vikerman

tools/bazel-stamp-vars.sh

@@ -4,8 +4,6 @@
 
 set -u -e -E -o pipefail
 
-echo "Running: $0" >&2
-
 function onError {
   echo "Failed to execute: $0"
   echo ""