Below code snippet can be helpful if you are using Databricks CLI
for jobid in `databricks jobs list | awk '{print $1}'`;
do databricks jobs get --job-id $jobid | jq .settings > /tmp/jobs/$jobid.json; done
sed -i 's/"spark_version": ".*"/"spark_version": "6.4.x-scala2.11"/g' *
for jobid in `databricks jobs list | awk '{print $1}'`; do
databricks jobs reset --job-id $jobid --json-file /tmp/jobs/$jobid.json;
done