Reenable log4j1 tests for Java 21

[meiao]

Description

MDC does not seem to work in Log4J1 when using Java 21.
That feature does not work with Java 1, but the logic to check if it is running in Java 1 is flawed.
https://github.com/apache/logging-log4j1/blob/b7e9154128cd4ae1244c877a6fda8f834a0f2247/src/main/java/org/apache/log4j/helpers/Loader.java#L42-L50

Because of this, the tests that check the MDC functionality fail in Java 21. Thus they have been disabled for Java 21.

It is likely that the functionality will work with Java 21.0.1, so we should reenable the tests then.

Acceptance Criteria

Either:

• the tests run and pass;
• add a comment explaining that that functionality will no longer work.

[workato-integration]

https://issues.newrelic.com/browse/NR-170086

[workato-integration]

https://new-relic.atlassian.net/browse/NR-180821