Fixed Issues in Zeppelin

Review the list of Zeppelin issues that are resolved in Cloudera Runtime 7.1.9 SP1.

CDPD-68796: Zeppelin - Upgrade Apache Maven to 3.8.6 due to CVE-2021-26291

Upgraded to Apache Maven 3.8.6 to resolve CVE-2021-26291 by no longer following HTTP (non-SSL) repository references in POM files, thereby mitigating the risks of malicious code injection.