Bump log4jVersion from 2.20.0 to 2.21.0

Bumps `log4jVersion` from 2.20.0 to 2.21.0.

Updates `org.apache.logging.log4j:log4j-slf4j-impl` from 2.20.0 to 2.21.0

Updates `org.apache.logging.log4j:log4j-core` from 2.20.0 to 2.21.0

---
updated-dependencies:
- dependency-name: org.apache.logging.log4j:log4j-slf4j-impl
  dependency-type: direct:development
  update-type: version-update:semver-minor
- dependency-name: org.apache.logging.log4j:log4j-core
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

pom.xml

@@ -100,7 +100,7 @@ under the License.
     <mavenVersion>3.5.4</mavenVersion>
     <cassandraVersion>3.11.16</cassandraVersion>
     <slf4jVersion>1.7.36</slf4jVersion>
-    <log4jVersion>2.20.0</log4jVersion>
+    <log4jVersion>2.21.0</log4jVersion>
     <commonsLoggingVersion>1.2</commonsLoggingVersion>
     <buildHelperPluginVersion>3.3.0</buildHelperPluginVersion>
     <project.build.outputTimestamp>2022-04-17T09:02:12Z</project.build.outputTimestamp>