Bump org.apache.maven.plugins:maven-javadoc-plugin from 3.6.3 to 3.8.0 #5139

Job	Run time
build-all	2m 59s
tests (hbase, -Dtest="*/diskstorage/hbase/", hbase2-diskstorage-java8, 8)	30m 29s
tests (hbase, -Dtest="*/graphdb/hbase/", hbase2-graphdb-java8, 8)	30m 50s
tests (hbase, -Dtest="*/hadoop/", hbase2-hadoop-java8, 8)	10m 51s
tests (hbase, -Pjava-11, -Dtest="*/diskstorage/hbase/", hbase2-diskstorage, 11)	22m 49s
tests (hbase, -Pjava-11, -Dtest="*/graphdb/hbase/", hbase2-graphdb, 11)	36m 53s
tests (hbase, -Pjava-11, -Dtest="*/hadoop/", hbase2-hadoop, 11)	12m 19s
	2h 27m 10s

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