Bump org.apache.logging.log4j:log4j-core from 2.1 to 2.12.4 in /core

Bumps org.apache.logging.log4j:log4j-core from 2.1 to 2.12.4.

---
updated-dependencies:
- dependency-name: org.apache.logging.log4j:log4j-core
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

core/pom.xml

@@ -65,7 +65,7 @@
     <dependency>
     	<groupId>org.apache.logging.log4j</groupId>
     	<artifactId>log4j-core</artifactId>
-    	<version>2.1</version>
+    	<version>2.12.4</version>
     	<scope>test</scope>
     </dependency>
   </dependencies>