To minimize risk and potential security vulnerabilities, upgrade your Web Apps to Tomcat 8.5 or 9 depending on your workload requirements.
To start, log in to Azure portal, navigate to the web app(s) go to Configuration > Settings > Stack Settings. You will see dropdowns for Tomcat versions. Select Tomcat 8.5 or 9.0.
You can also view other resources before you upgrade your Web Apps to Tomcat 8.5 or 9.
If you have any additional queries regarding this retirement, please use comments on this thread to ask your specific queries and we will try our best to answer those queries.