Remove support for H2 due to 3rd-party vulnerability issue CVE-2021-23463

Current Situation

• Currently JobScheduler Master ships with an H2 JDBC Driver h2-1.3.170.jar
• The JDBC Driver is not used for access to the JobScheduler database but can be used for access to H2 databases, for example with JITL jobs.
• a vulnerability affects this version,
  • see https://cve.mitre.org/cgi-bin/cvename.cgi?name=2021-23463

Desired Behavior

• The JDBC Driver is removed from the JobScheduler Master.
• Users who want to access H2 databases can download the respective H2 JDBC Driver and add the .jar file to the ./lib/jdbc directory of the Master.