Bump version.log4j from 2.12.4 to 2.21.0 (#3366)

* Bump version.log4j from 2.12.4 to 2.21.0

Bumps `version.log4j` from 2.12.4 to 2.21.0.

Updates `org.apache.logging.log4j:log4j-core` from 2.12.4 to 2.21.0

Updates `org.apache.logging.log4j:log4j-slf4j-impl` from 2.12.4 to 2.21.0

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

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

* Update pom.xml

* Update pom.xml

---------

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Jonas Kunz <[email protected]>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

apm-agent-plugins/apm-ecs-logging-plugin/pom.xml

@@ -48,7 +48,7 @@
         <dependency>
             <groupId>org.apache.logging.log4j</groupId>
             <artifactId>log4j-core</artifactId>
-            <version>2.20.0</version>
+            <version>2.21.0</version>
             <scope>provided</scope>
             <optional>true</optional>
         </dependency>