How to change e-mail alert content type to plaintext?

What Grafana version and what operating system are you using?
Using Grafana version 9 installed in RHEL instance.
What are you trying to achieve?
change e-mail alert content type to plaintext
How are you trying to achieve it?
I am working on integration of Grafana alerts with ServiceNow and need to switch the alert format to plaintext. I found this issue but am not able to switch the format
What did you expect to happen?
To have Grafana e-mail alerts in plaintext format.

Thank you!