Fully rely on Dependabot for Tomcat version update

Currently, the Tomcat version update is handled by the check-tomcat-update job for 2021 and 2023.

Yet, in 2023, the Dependabot version updates are also opening PRs to update Tomcat, such as this one.

To avoid such duplicates, we could remove the job and rely only on Dependabot.
This should already work for 2023 with version updates.
For 2021, we would need to enable version updates with a configuration to open only PRs to update Tomcat.