QPIDJMS-556: update test+examples slf4j-log4j dep to 2.15.0
QPIDJMS-556: update test+examples slf4j-log4j dep to 2.15.0

apache/qpid-jms,tabish121/qpid-jms,tabish121/qpid-jms,gemmellr/qpid-jms,apache/qpid-jms,gemmellr/qpid-jms