RATIS-1467. Remove unused log4j dependency from pom.xml.

[szetszwo]

See https://issues.apache.org/jira/browse/RATIS-1467

[adoroszlai]

The dependency change looks good.

Note that ratis-hadoop has transitive dependency on log4j (via hadoop-common). I guess that's OK.

Should we also remove the log4j-related info below?

ratis/ratis-resource-bundle/src/main/resources/supplemental-models.xml

Lines 1155 to 1168 in a7555cf

	<supplement>
	<project>
	<groupId>log4j</groupId>
	<artifactId>log4j</artifactId>
	<licenses>
	<license>
	<name>Apache License, Version 2.0</name>
	<url>http://www.apache.org/licenses/LICENSE-2.0.txt</url>
	<distribution>repo</distribution>
	</license>
	</licenses>
	</project>
	</supplement>

[szetszwo]

Should we also remove the log4j-related info below?

Let's keep the license in supplemental-models.xml, which includes licenses for transitive dependencies.

[szetszwo]

@adoroszlai , thanks a lot for reviewing this.