Bump log4j.version from 2.20.0 to 2.21.1

Bumps `log4j.version` from 2.20.0 to 2.21.1.

Updates `org.apache.logging.log4j:log4j-api` from 2.20.0 to 2.21.1

Updates `org.apache.logging.log4j:log4j-core` from 2.20.0 to 2.21.1

---
updated-dependencies:
- dependency-name: org.apache.logging.log4j:log4j-api
  dependency-type: direct:production
  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] <support@github.com>

pom.xml

@@ -29,7 +29,7 @@
         <restlet.version>2.4.3</restlet.version>
         <jetty.version>10.0.13</jetty.version>
         <jackson.version>2.15.3</jackson.version>
-        <log4j.version>2.20.0</log4j.version>
+        <log4j.version>2.21.1</log4j.version>
     </properties>
 
     <repositories>