Bump log4j from 2.20.0 to 2.21.0

Bumps `log4j` from 2.20.0 to 2.21.0.

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

Updates `org.apache.logging.log4j:log4j-jul` from 2.20.0 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-jul
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -14,7 +14,7 @@ junit4 = "4.13.2"
 junit4Osgi = "4.13.2_1"
 junit4Min = "4.12"
 ktlint = "0.48.2"
-log4j = "2.20.0"
+log4j = "2.21.0"
 opentest4j = "1.3.0"
 openTestReporting = "0.1.0-M1"
 surefire = "3.1.2"